Segmental copolymers and aqueous dispersions and films therefrom

ABSTRACT

An aqueous dispersion of a segmental copolymer, wherein the aqueous dispersion has a Hard/Soft Balance Advantage value of at least 25% is disclosed. A method for preparing the aqueous dispersion of a segmental copolymer is also disclosed, as is a film produced thereby.

This application is a continuation-in-part of Ser. No. 60/232,414, filedSep. 14, 2000.

The present invention relates to an aqueous dispersion of a segmentalcopolymer, wherein films formed from the aqueous dispersion display animproved balance of properties related to hardness and softness, and tothe segmental copolymer of which the aqueous dispersion is comprised.

Polymeric films are typically formed by deposition of a solution ordispersion of a polymer in a solvent or dispersing medium, respectively.Evaporation of the layer thus formed will result in a continuous filmfor some polymer compositions, but not for others. For example, adispersion including polymeric particles, the polymeric chains of whichhave a glass transition temperature in the range of −40° C. to 70° C.,may form a continuous film, with the likelihood of such formationincreasing for polymers having Tg values near, or below, the temperatureat which film formation is attempted, often room temperature.Unfortunately, films that are easily formed often exhibit poor hardnessrelated properties. They tend to be “soft” and tacky. This tackinesstranslates into a tendency for the surface of the film to retain dirtparticles that contact it. Tackiness also translates into “block”, thetendency for two films to stick to one another, or for a single film tostick to itself. The softness further translates into unrecoverabledeformation, called “print”. “Print” is observed when an object isplaced upon a film and, upon removal, the imprint of the object does notgo away.

It is, therefore, highly desirable to form films that have a “hardness”component. This hardness translates into films having surfaces thatresist scratching, dirt pick-up, and block. Truly “hard” films aredifficult to achieve because the relatively high glass transitiontemperature, “Tg”, required to produce such films renders the actualformation of films difficult or impossible. When these “hard” films areachieved, for example, by adding high levels of a coalescent to anaqueous dispersion of a hard polymer, these films often are so dominatedby the hardness characteristic that they fail to exhibit softnesscharacteristics that can contribute to overall performance of the film.Hard films are often brittle films lacking the flexibility to elongateand bend, especially at low temperature (i.e., below 20° C.), a commonrequirement during use.

The invention of U.S. Pat. No. 6,060,532 sought, for example, to providecoatings having a good balance of low temperature flexibility, tensilestrength, and dirt pick up resistance. Low temperature flexibility is a“softness” characteristic, while tensile strength and dirt pick upresistance are characteristic of “hardness”. Coatings were formed from abinder polymer which was an elastomeric multi-stage emulsion polymerobtained by sequentially polymerizing, under emulsion polymerizationconditions, a first monomer system free from polyethylenicallyunsaturated monomers, and which yields a first-stage polymer having aglass transition temperature from about −30° C. to about −60° C., and asecond monomer system, likewise free from polyethylenically unsaturatedmonomers, and which yields a second-stage polymer, incompatible with thefirst-stage polymer, and having a glass transition temperature from 0°C. to 60° C. Used herein, these two-stage polymers are referred to a“soft/hard elastomers”, or “SHE” polymers. While the SHE polymers ofU.S. Pat. No. 6,060,532 did improve the balance of hard and softproperties over that of single stage polymers having similar overallcompositions, there remained a need for yet further improvement in thehard/soft balance. It was further desired to achieve that improvementwhile maintaining excellent film formation behavior for aqueous bindersystems completely free of coalescing agents, or containing only lowlevels of them.

We have, surprisingly, found that aqueous dispersions of segmentalcopolymers can be formed into films having an outstanding balance ofproperties related to hardness and softness. In particular, we have beenable to produce comb copolymers and aqueous dispersions of combcopolymers by a commercially viable method and form them into filmshaving an outstanding balance of properties related to hardness andsoftness. The polymers can, for example, be utilized in films cast ontosubstrate surfaces and in free standing films.

A first aspect of the present invention relates to an aqueousdispersion, comprising at least one segmental copolymer, wherein saidaqueous dispersion has a Hard/Soft Balance Advantage value of at least25%.

A second aspect of the present invention relates to a method of forminga film comprising the steps of:

(a) forming an aqueous dispersion of a segmental polymer;

(b) applying said aqueous dispersion to a substrate; and

(c) drying, or allowing to dry, said applied aqueous dispersion;

wherein said aqueous dispersion has a Hard/Soft Balance Advantage valueof at least 25%.

A third aspect of the present invention relates to a method of forming afilm comprising the steps of:

(a) forming an aqueous dispersion comprising a plurality of combcopolymer particles:

wherein said comb copolymer particles comprise a comb copolymer; and

wherein said comb copolymer comprises a backbone and at least one graftsegment attached thereto;

(b) applying said aqueous dispersion to a substrate; and

(c) drying, or allowing to dry, said applied aqueous dispersion;

wherein said aqueous dispersion has a Hard/Soft Balance Advantage valueof at least 25%.

A fourth aspect of the present invention relates to a film produced bythe method of either the second aspect or the third aspect.

A further aspect relates to an aqueous dispersion wherein the combcopolymer is produced by a polymerization method comprising the stepsof:

(a) forming a macromonomer aqueous emulsion comprising a plurality ofwater-insoluble particles of macromonomer, wherein said macromonomercomprises polymerized units of at least one first ethylenicallyunsaturated monomer, said macromonomer further having:

(i) a degree of polymerization of from 10 to 1000;

(ii) at least one terminal ethylenically unsaturated group;

(iii) less than 5 weight percent polymerized acid-containing monomer,based on the weight of said macromonomer; and

(iv) less than one mole percent of polymerized mercaptan-olefincompounds;

(b) forming a monomer composition comprising at least one secondethylenically unsaturated monomer; and

(c) combining at least a portion of said macromonomer aqueous emulsionand at least a portion of said monomer composition to form apolymerization reaction mixture; and

(d) polymerizing said macromonomer with said second ethylenicallyunsaturated monomer in the presence of an initiator to produce saidplurality of comb copolymer particles.

In a still further aspect, the comb copolymer has a weight averagemolecular weight of 50,000 to 2,000,000.

In yet another aspect, the graft segment of the comb copolymer isderived, as a polymerized unit, from a macromonomer; wherein the graftsegment comprises, as polymerized units, from 5 weight percent to 50weight percent of a non-methacrylate monomer, based on the weight of themacromonomer.

In another aspect, the graft segment of the comb copolymer is derived,as a polymerized unit, from a macromonomer; wherein the graft segmentcomprises, as polymerized units, less than 5 weight percent acidcontaining monomer, based on the total weight of said macromonomer.

In another aspect, the graft segment of the comb copolymer is derived,as a polymerized unit, from a macromonomer, wherein said graft segmenthas a degree of polymerization of from 10 to 1,000, where the degree ofpolymerization of said graft segment is expressed as the degree ofpolymerization of said macromonomer.

In another aspect, the graft segment of the comb copolymer has a glasstransition temperature of 30° C. to 130° C.

In another aspect, the backbone of the comb copolymer has a glasstransition temperature of −90° C. to 50° C.

Used herein, the following terms have these definitions:

The “backbone” of a polymer chain is a collection of polymerized monomerunits attached to one another. The attachment is typically achieved bycovalent bonding. “Non-terminal” monomer units are directly attached toat least two other monomer units. A “terminal” monomer unit resides atthe end of the polymer chain and is directly attached to one othermonomer unit. For example, the polymerized monomer units of the backbonemay be derived from ethylenically unsaturated monomers.

A “linear” polymer (homopolymer or copolymer) is a polymer having abackbone that is not branched. As used herein, the term “linear” is alsomeant to include polymers wherein a minor amount of branching hasoccurred. For example, hydrogen abstraction may lead to branching duringfree radical polymerizations.

A “branched” polymer is a polymer having a first “backbone segment” thathas other backbone segments (i.e., “branches”) chemically attached to itthrough a “non-terminal” atom of the first backbone segment. Typically,this first backbone segment and all of the branches have the same, orsimilar, composition. Herein, the term “branching” is used to describethe structure of the backbone of the comb copolymer.

A “pendant” group is a group that is attached to the backbone of apolymer. The term pendant may be used to describe a group that isactually part of a polymerized monomer unit. For example, thehydroxyethyl group of a polymerized unit of 2-hydroxyethyl methacrylatemay be referred to as a “pendant hydroxyethyl group”, or as “pendanthydroxy functionality”. It is also common to refer to large groupsattached to a polymer backbone as “pendant” when those large groups arecompositionally distinct from the backbone polymer. These large groupsmay themselves be polymer chains. For example, when a macromonomerbecomes incorporated into a polymer chain by reaction with othermonomers, the two carbons of its reactive double bond become part of thebackbone, while the polymeric chain originally attached to the doublebond of the macromonomer becomes a “pendant group” that may, forexample, have a molecular weight of 500 to 100,000. A “pendant” groupmay further be described as “pendant to” the backbone.

A “terminal” group resides at the end of the polymer chain and ischemically attached to a terminal monomer unit. A terminal group may,for example, have a composition distinct from the composition of thebackbone of the polymer. A “pendant” group may occur in a “terminal”position. As such, a “terminal” group is a special case of a “pendant”group.

A “macromonomer” of the present invention is any low molecular weightwater-insoluble polymer or copolymer having at least one terminalethylenically unsaturated group that is capable of being polymerized ina free radical polymerization process. The macromonomer of the presentinvention preferably has “low water solubility”. By “low watersolubility” it is meant having a water solubility of no greater than 150millimoles/liter at 25° C. to 50° C. In contrast the “acid containingmacromonomer”, described herein below, of the present invention is watersoluble. By “low molecular weight” it is meant that the macromonomer hasa degree of polymerization of from 5 to 1,000, preferably from 10 to1,000, more preferably 10 to 200, and most preferably from about 20 toless than 50. By “degree of polymerization” it is meant the number ofpolymerized monomer units present in the macromonomer. See e.g.,Kawakami in the “Encyclopedia of Polymer Science and Engineering”, Vol.9, pp. 195-204, John Wiley & Sons, New York, 1987. Typically, themacromonomer polymer chain contains first ethylenically unsaturatedmonomers, as polymerized units. Preferably, the first ethylenicallyunsaturated monomer is selected to impart low water solubility to themacromonomer. Although it is most preferred that every unit ofmacromonomer have at least one terminal ethylenically unsaturated groupthat is capable of being polymerized in a free radical polymerizationprocess, the percentage of macromonomer units having such a terminalethylenically unsaturated group is typically sufficient to prepare thedesired comb copolymer of the present invention when that percentage isless than 70%, preferably at less than 80%, and more preferably at lessthan 85%.

The term “macromonomer aqueous emulsion” is used herein to describe anaqueous emulsion containing macromonomer dispersed therein as waterinsoluble particles.

A “graft segment” is a polymer chain occupying a pendant position alongthe polymer backbone. A graft segment may include, as polymerized units,one type of monomer or more than one type of monomer. The composition ofa graft segment is different from the composition of the backbonepolymer to which it is attached, in contrast to a “branch segment” of abranched backbone which has a composition which is the same as, orsimilar to, other portions the branched backbone of which it is a part.A “terminal graft segment” resides at an end of a backbone polymer chainand is chemically attached to that backbone polymer chain. A “terminalgraft segment” is a special case of a “pendant graft segment”.

“Graft copolymers” are macromolecules formed when polymer or copolymerchains are chemically attached as side chains to a polymeric backbone.Those side chains are the “graft segments” described herein above.Because graft copolymers often chemically combine unlike polymericsegments in one macromolecule, these copolymers have unique propertiescompared to the corresponding random copolymer analogues. Theseproperties include, for example, mechanical film properties resultingfrom thermodynamically driven microphase separation of the copolymer,and decreased melt viscosities resulting in part from the segmentalstructure of the graft copolymer, and from separation of a soft (i.e.,low Tg) phase. With respect to the latter, reduced melt viscosities canadvantageously improve processability of the polymer. See e.g.,Hong-Quan Xie and Shi-Biao Zhou, J. Macromol. Sci.-Chem., A27(4),491-507 (1990); Sebastian Roos, Axel H. E. Müller, Marita Kaufmann,Werner Siol and Clenens Auschra, “Applications of Anionic PolymerizationResearch”, R. P. Quirk, Ed., ACS Symp. Ser. 696, 208 (1998). The graftcopolymer of the present invention is a comb copolymer. Herein, theterms “graft copolymer” and “comb copolymer” are used interchangeably.

The term “comb copolymer,” as used herein, is a type of graft copolymer,wherein the polymeric backbone of the graft copolymer is linear, oressentially linear, and, preferably, each side chain (graft segment) ofthe graft copolymer is formed by a “macromonomer” that is grafted to thepolymer backbone. The comb copolymers may, for example, be prepared bythe free radical copolymerization of macromonomer with conventionalmonomer (e.g., second ethylenically unsaturated monomer). Used herein, acomb copolymer may be one, or more than one type of comb copolymer,i.e., at least one comb copolymer.

A “block copolymer” is a copolymer having a backbone characterized bythe presence of two or more “blocks”. A “block” is a segment ofcopolymer backbone having a particular and distinct composition. Seee.g., G. Odian “Principles of Polymerization”, Third Edn., pp. 142-149,John Wiley & Sons, New York, 1991. For example, a block could becomposed entirely of styrene monomer, present as polymerized units. Atleast two blocks differing in composition must be present in a blockcopolymer, however, more than one block of a given composition may bepresent. For example, a poly(styrene)-b-poly(butadiene)-b-poly(styrene)has two poly(styrene) blocks joined by a poly(butadiene) block. Blocksare typically at least 10 monomer units, preferably at least 50 monomerunits, and more preferably at least 100 monomer units in length. Usedherein, the term block copolymer refers to one or more types of blockcopolymer, i.e., at least one block copolymer.

A “random copolymer” is a copolymer having monomers, as polymerizedunits, randomly distributed along its backbone. Used herein, the term“random” has its usual meaning in the art of polymerization. Forexample, the distribution of monomer units along a polymer chainprepared by emulsion polymerization is dictated not only by the relativeamounts of each type of monomer present at any point during thepolymerization, but also by such factors as, for example, the tendencyof each monomer type to react with itself relative to its tendency toreact with each of the other types of monomer present. These reactivetendencies are defined by reactivity ratios which are well know for manymonomer combinations. See e.g., G. Odian “Principles of Polymerization”,Third Edn., pp. 460-492, John Wiley & Sons, New York, 1991.

The term “segmental copolymer” includes “block copolymers” and “combcopolymers”. Used herein, the term segmental copolymer refers to one ormore types of segmental copolymer, i.e., at least one segmentalcopolymer.

The term “SHE copolymer” refers to a “soft/hard elastomer” which is amulti-stage copolymer prepared by sequentially polymerizing, underemulsion polymerization conditions, first monoethylenically unsaturatedmonomers to yield a first-stage polymer having a Tg of −60° C. to −30°C., and then polymerizing second monoethylenically unsaturated monomersto yield a second-stage polymer having a Tg of 0° C. to 60° C. The SHEcopolymer further includes low levels (up to 5 percent by weight, basedon total copolymer) of either a photosensitive benzophenone orphenylketone compound, or a photosensitive benzophenone monomer, aspolymerized units. The SHE copolymers referred to herein are disclosedin U.S. Pat. No. 6,060,532.

An “oligomer” is a polymer having a low molecular weight. By “lowmolecular weight” it is meant that the oligomer has a degree ofpolymerization of from 5 to 1,000, preferably from 10 to 1,000, morepreferably 10 to 200, and most preferably from about 20 to less than 50.

An “aqueous dispersion of a segmental copolymer” is an aqueous medium inwhich are dispersed a plurality of particles of segmental copolymer.Used herein, an “aqueous dispersion of a segmental copolymer” is an“aqueous copolymer composition”.

“Tg” is the “glass transition temperature” of a polymeric phase. Theglass transition temperature of a polymer is the temperature at which apolymer transitions from a rigid, glassy state at temperatures below Tgto a fluid or rubbery state at temperatures above Tg. The Tg of apolymer is typically measured by differential scanning calorimetry (DSC)using the mid-point in the heat flow versus temperature transition asthe Tg value. A typical heating rate for the DSC measurement is 20Centigrade degrees per minute. The Tg of various homopolymers may befound, for example, in Polymer Handbook, edited by J. Brandrup and E. H.Immergut, Interscience Publishers. The Tg of a copolymer is estimated byusing the Fox equation (T. G. Fox, Bull. Am. Physics Soc., Volume 1,Issue No. 3, page 123 (1956)). A two-phase system resulting from theformation of a film from a segmental copolymer having two types ofsegment, each immiscible with the other, typically yields two measurableglass transition temperatures. For such a comb copolymer, one Tg can bemeasured, or calculated, for the phase formed by the backbone, andanother Tg for the phase formed by the graft segment. An “average Tg”,or “overall Tg” may be calculated for such systems as a weighted averageof the amount of polymer in each phase of a given Tg. This average Tgfor a two-phase system will equal the single Tg calculated for a randomcopolymer having the same overall composition as that of a copolymer forwhich two Tg values may be calculated or measured.

When a substance (e.g., a coalescent) having some degree of solubilityin a polymer is imbibed by that polymer, the softening temperature ofthe polymer decreases. This plasticization of the polymer can becharacterized by measuring the “effective Tg” of the polymer, whichtypically bears an inverse relationship to the amount of solvent orother substance contained in the polymer. The “effective Tg” of apolymer containing a known amount of a substance dissolved within ismeasured just as described above for “Tg”. Alternatively, the “effectiveTg” may be estimated by using the Fox equation (supra), assuming a valuefor Tg (e.g., the freezing point) of the solvent or other substancecontained in the polymer.

Synthetic polymers are almost always a mixture of chains varying inmolecular weight, i.e., there is a “molecular weight distribution”,abbreviated “MWD”. For a homopolymer, members of the distribution differin the number of monomer units which they contain. This way ofdescribing a distribution of polymer chains also extends to copolymers.Given that there is a distribution of molecular weights, the mostcomplete characterization of the molecular weight of a given sample isthe determination of the entire molecular weight distribution. Thischaracterization is obtained by separating the members of thedistribution and then quantitating the amount of each that is present.Once this distribution is in hand, there are several summary statistics,or moments, which can be generated from it to characterize the molecularweight of the polymer.

The two most common moments of the distribution are the “weight averagemolecular weight”, “M_(w)”, and the “number average molecular weight”,“M_(n)”. These are defined as follows:

M _(w)=Σ(W _(i) M _(i))/ΣW _(i)=Σ(N _(i) M _(i) ²)/ΣN _(i) M _(i)

M _(n) =ΣW _(i)/Σ(W _(i) /M _(i))=Σ(N _(i) M _(i))/ΣN _(i)

where:

M_(i)=molar mass of i^(th) component of distribution

W_(i)=weight of i^(th) component of distribution

N_(i)=number of chains of i^(th) component

and the summations are over all the components in the distribution.M_(w) and M_(n) are typically computed from the MWD as measured by GelPermeation Chromatography (see the Experimental Section).

“Particle size” is the diameter of a particle.

The “average particle size” determined for a collection of particles(e.g., macromonomer particles, or particles of graft copolymer) the“weight average particle size”, “d_(w)”, as measured by CapillaryHydrodynamic Fractionation technique using a Matec CHDF 2000 particlesize analyzer equipped with a HPLC type Ultra-violet detector.

The “Advantage term”, designated “A” herein, is a term that defines theperformance of an aqueous dispersion of a polymer (herein the polymer istypically a segmental copolymer, preferably a comb copolymer) in aspecific test, or a battery of tests, relative to a control, which is anaqueous dispersion of a random copolymer having the same overallcomposition as the segmental copolymer with which it is being compared.The advantage term for performance in a single test is defined asfollows:

A=[(P/P _(control))−1]×100%,

where P is the performance of a first material, as an aqueousdispersion, in a given test, and P_(control) is the performance in thesame test of another material, as an aqueous dispersion, with which thatfirst material is being compared. The value of an “Advantage term” isreferred to as the corresponding “Advantage value”, given in units ofpercent. In determining the value of the Advantage term (i.e., the“Advantage value”) for an aqueous dispersion of a given segmentalcopolymer, the control aqueous dispersion is that of a random copolymerhaving the same overall composition as the segmental copolymer beingcompared to it, and present in the aqueous dispersion at the sameconcentration as the segmental copolymer. When the “Advantage value” foran aqueous dispersion of a polymer-polymer or polymer-oligomer blend isdetermined herein, the control polymer is an aqueous dispersion of arandom copolymer having the same overall composition as the blend. Forexample, a 50:50 (weight:weight) blend of polymer A composed of, aspolymerized units, 30 mole percent of monomer X and 70 mole % of monomerY, with polymer B composed of, as polymerized units, only monomer Y,would be compared with a random copolymer having 15 mole % of monomer Xand 85 mole % of monomer Y.

Four tests measuring “hardness” are described herein and utilized todifferentiate among various copolymers (as aqueous dispersions) in theExperimental Section herein below. “A_(K)”, “A_(T)”, “A_(S)”, and“A_(B)” are the advantage terms derivable from the “Konig PendulumHardness”, “Finger Tack”, “Tensile Strength”, and “Peel BlockResistance” tests, respectively. As such, they are referred to as the“Konig Hardness Advantage term”, the “Tack Advantage term”, the “TensileStrength Advantage term”, and the “Block Advantage term”, respectively.Used herein, “Konig” and “Konig Hardness” may be used interchangeablywith “Konig Pendulum Hardness”; “Tack” may be used interchangeably with“Finger Tack”, and “Block” and “Block Resistance” may be usedinterchangeably with “Peel Block Resistance”.

Two tests measuring “softness” are described herein and utilized todifferentiate among various copolymers (as aqueous dispersions) in theExperimental Section herein below. “A_(E)”, and “A_(F)” are theadvantage terms derivable from the tensile elongation test and the lowtemperature mandrel flexibility test, respectively. As such, they arereferred to as the “Elongation Advantage term” and the “FlexibilityAdvantage term”, respectively. The temperature selected for the mandrelflexibility test is chosen to be equal to or less than the overall glasstransition temperature, Tg, of the copolymer film being tested. Thistemperature is chosen, herein, to be −35° C., unless specifiedotherwise.

For any given material, the average of the experimentally determinedvalues for the four “hardness” advantage terms are averaged to give the“Hardness Advantage Term”, “A_(Hard)”. Similarly, the average of theexperimentally determined values for the two “softness” advantage termsare averaged to give the “Softness Advantage Term”, “A_(Soft)”.“A_(Hard)” and “A_(Soft)” are then averaged to give “A_(HSB)”, the“Hard/Soft Balance Advantage term”, abbreviated herein as “A_(HSB)”. Thefollowing expressions define “A_(Hard)”, “A_(Soft)”, and “A_(HSB)”:

 A _(Hard)=(A _(K) +A _(T) +A _(S) +A _(B))/4;

A _(Soft)=(A _(E) +A _(F))/2; and

A _(HSB)=(A _(Hard) +A _(Soft))/2.

In any equation for an Advantage term used herein to describeperformance in a given test, it is assumed that “P” and “P_(control)”(see the general equation for “A” above) are measured by that testmethod, so that there is no need to provide additional subscripts forthose performance terms.

When a material does not form a film under the conditions of filmformation used in preparing specimens for the tests, each advantage termis assigned a value of −100%. In such cases, “A_(HSB)” also becomes−100%. “A_(HSB)” is then a good measure of the three-way balance of filmhardness, film softness, and the ability to form a film.

The segmental copolymers of the present invention preferably haveHard/Soft Balance Advantage Values of at least 25%, more preferably from40% to 1,500%, and most preferably from 100% to 1,000%.

Estimation of whether a polymer and another component (i.e., anotherpolymer or a solvent) will be miscible may be made according to thewell-known methods delineated in D. W. Van Krevelen, Properties ofPolymers, 3^(rd) Edition, Elsevier, pp. 189-225, 1990. For example, VanKrevelen defines the total solubility parameter (δ_(t)) for a substanceby:

δ_(t) ²=δ_(d) ²+δ_(p) ²+δ_(h) ²,

where δ_(d), δ_(p), and δ_(h) are the dispersive, polar, and hydrogenbonding components of the solubility parameter, respectively. Values forδ_(d), δ_(p), and δ_(h) have been determined for many solvents,polymers, and polymer segments, and can be estimated using the groupcontribution methods of Van Krevelen. For example, to estimate whether apolymer having a given composition will be miscible with a particularsolvent, one calculates δ_(t) ² for the polymer and δ_(t) ² for thesolvent. Typically, if the difference between the two, Δδ_(t) ², isgreater than 25 (i.e., Δδ_(t)>5), then the polymer and the solvent willnot be miscible.

If, instead, it is desired to determine whether two polymers, differingin composition, will be miscible, the same calculations may be carriedout, but the predicted upper limit of Δδ_(t) ² for miscibility willdecrease as the molecular weight of one or both of polymers underconsideration increases. This decrease is thought to parallel thedecrease in entropy of mixing which occurs as the molecular weight ofthe components being mixed increases. For example, two polymers, eachhaving a degree of polymerization of 100, will likely be immiscible evenif the value of Δδ_(t) ² for their mixture is 9, or even 4 (i.e.,Δδ_(t)=3, or even 2). Still higher molecular weight polymers may beimmiscible at even lower values of Δδ_(t) ². To estimate whether a graftsegment of a comb copolymer of the present invention, having a givencomposition, will be miscible with a backbone having anothercomposition, one calculates δ_(t) ² for the graft segment and δ_(t) ²for the backbone. Typically, if the difference between the two, Δδ_(t)², is greater than 9 (i.e., Δδ_(t)>3), then the graft segment should beimmiscible with the backbone such that a film formed by the combcopolymer would have two distinct types of polymeric phase. It should benoted, however, that immiscibility between two polymers having degreesof polymerization of approximately 100 or more may occur even when thecalculated value of Δδ_(t) ², is between 1 and 9 (i.e., Δδ_(t) of 1 to3), due to the unfavorable entropy effects associated with very longpolymeric chains. Similar calculation can be performed to determinewhether a film formed from a block copolymer will have more than onepolymeric phase. Because it is desirable that the graft segment not bemiscible with the backbone, the Van Krevelen calculations of miscibilityprovide useful estimates of whether a given pair of compositions of thegraft segment and backbone will result in phase separation in, forexample, films formed from the segmental copolymer.

A preferred method of preparing the graft copolymers of the presentinvention and their aqueous dispersions is by emulsion polymerization. Apreferred process for this preparation includes (a) forming, bypolymerization of at least one first ethylenically unsaturated monomer,a macromonomer aqueous emulsion containing one or more water-insolubleparticles of macromonomer; (b) forming a monomer composition containingat least one second ethylenically unsaturated monomer; and (c) combiningat least a portion of the macromonomer aqueous emulsion and at least aportion of the monomer composition to form a “polymerization reactionmixture”. The macromonomer and second ethylenically unsaturated monomerare polymerized in the presence of an initiator to form graft copolymerparticles.

The macromonomer of the present invention is present in the macromonomeraqueous emulsion as water insoluble particles. The macromonomer is anylow molecular weight water-insoluble polymer or copolymer having atleast one terminal ethylenically unsaturated group that is capable ofbeing polymerized in a free radical polymerization process.

The macromonomer contains, as polymerized units, at least one firstethylenically unsaturated monomer. Preferably, the first ethylenicallyunsaturated monomer is selected to impart low or no water solubility tothe macromonomer as previously described herein.

Suitable first ethylenically unsaturated monomers for use in preparingmacromonomer include for example methacrylate esters, such as C₁ to C₁₈normal or branched alkyl esters of methacrylic acid, including methylmethacrylate, ethyl methacrylate, n-butyl methacrylate, laurylmethacrylate, stearyl methacrylate; acrylate esters, such as C₁ to C₁₈normal or branched alkyl esters of acrylic acid, including methylacrylate, ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate;styrene; substituted styrenes, such as methyl styrene, a-methyl styreneor t-butyl styrene; olefinically unsaturated nitrites, such asacrylonitrile or methacrylonitrile; olefinically unsaturated halides,such as vinyl chloride, vinylidene chloride or vinyl fluoride; vinylesters of organic acids, such as vinyl acetate; N-vinyl compounds suchas N-vinyl pyrrolidone; acrylamide; methacrylamide; substitutedacrylamides; substituted methacrylamides; hydroxyalkylmethacrylates suchas hydroxyethylmethacrylate; hydroxyalkylacrylates; basic substituted(meth)acrylates and (meth)acrylamides, such as amine-substitutedmethacrylates including dimethylaminoethyl methacrylate,tertiary-butylaminoethyl methacrylate and dimethylaminopropylmethacrylamide and the likes; dienes such as 1,3-butadiene and isoprene;vinyl ethers; or combinations thereof. The term “(meth)”, i.e., withparentheses, as used herein means that the “meth” is optionally present.For example, “(meth)acrylate” means methacrylate or acrylate.

The first ethylenically unsaturated monomer can also be a functionalmonomer including for example monomers containing hydroxy, amido,aldehyde, ureido, polyether, glycidylalkyl, keto functional groups orcombinations thereof. These functional monomers are generally present inthe macromonomer at a level of from 0.1 weight percent to 15 weightpercent and more preferably from 0.5 weight percent to 10 weightpercent, and most preferably from 1.0 to 3 weight percent, based on thetotal weight of the graft copolymer. Used herein, all ranges areinclusive and combinable. Examples of functional monomers includeketofunctional monomers such as the acetoacetoxy esters of hydroxyalkylacrylates and methacrylates (e.g., acetoacetoxyethyl methacrylate) andketo-containing amides (e.g., diacetone acrylamide); allyl alkylmethacrylates or acrylates; glycidylalkyl methacrylates or acrylates; orcombinations thereof. Such functional monomers can provide crosslinkingif desired.

Typically, the macromonomer also contains as polymerized units less than10 weight percent, preferably less than 5 weight percent, morepreferably less than 2 weight percent, and most preferably less thanless than 1 weight percent acid containing monomer, based on the totalweight of the macromonomer. In a most preferred embodiment, themacromonomer contains no acid containing monomer. Used herein, “acidcontaining monomer” and “acid functional monomer” are usedinterchangeably. By “acid containing monomer” it is meant anyethylenically unsaturated monomer that contains one or more acidfunctional groups or functional groups that are capable of forming anacid (e.g., an anhydride such as methacrylic anhydride or tertiary butylmethacrylate). Examples of acid containing monomers include, forexample, carboxylic acid bearing ethylenically unsaturated monomers suchas acrylic acid, methacrylic acid, itaconic acid, maleic acid andfumaric acid; acryloxypropionic acid and (meth)acryloxypropionic acid;sulphonic acid-bearing monomers, such as styrene sulfonic acid, sodiumvinyl sulfonate, sulfoethyl acrylate, sulfoethyl methacrylate,ethylmethacrylate-2-sulphonic acid, or 2-acrylamido-2-methylpropanesulphonic acid; phosphoethylmethacrylate; the corresponding salts of theacid containing monomer; or combinations thereof.

The macromonomer may contain, as a polymerized unit, a “non-methacrylatemonomer”. Used herein, a “non-methacrylate monomer” is any firstethylenically unsaturated monomer that is not a methacrylate. Forexample, butyl acrylate is a first ethylenically unsaturated monomerthat is a non-methacrylate monomer. The macromonomer may be free ofnon-methacrylate monomer, but typically it contains, as polymerizedunits, at least one non-methacrylate monomer unit, preferably 5 weightpercent to 50 weight percent non-methacrylate monomer, more preferably10 weight percent to 35 weight percent non-methacrylate monomer, andmost preferably 15 weight percent to 25 weight percent ofnon-methacrylate monomer, based on the weight of the macromonomer.

The macromonomer also contains, as polymerized units, less than 1 molepercent, preferably less than 0.5 mole percent, and more preferably nomercapto-olefin compounds, based on the total moles of monomer, presentas polymerized units, in the macromonomer. Used herein,“mercapto-olefin” and “mercaptan-olefin” are used interchangeably. Thesemercapto-olefin compounds are those as disclosed in U.S. Pat. No.5,247,000 by Amick. The mercapto-olefin compounds described in Amickhave ester functional groups, which are susceptible to hydrolysis.

In a preferred embodiment of the present invention, the macromonomer iscomposed of 50 weight percent to 95 weight percent, more preferably from65 to 90 weight percent, and most preferably from 75 to 85 weightpercent, based on total weight of macromonomer, of at least one α-methylvinyl monomer, a non α-methyl vinyl monomer terminated with an α-methylvinyl monomer, or combinations thereof. The macromonomer may even becomposed of 100 weight percent α-methyl vinyl monomers, non α-methylvinyl monomers terminated with α-methyl vinyl monomers, or combinationsthereof, based on the total weight of the macromonomer. The phrase “nonα-methyl vinyl monomer terminated with an α-methyl vinyl monomer” meansthat, when a vinyl monomer bearing no α-methyl group is present, aspolymerized units, in the macromonomer, the macromonomer must beterminated by a unit derived from an α-methyl vinyl monomer. Forexample, while styrene might be present, as polymerized units, in amacromonomer chain, that macromonomer chain would be terminated byα-methyl styrene, or some other α-methyl vinyl monomer. Suitableα-methyl vinyl monomers include, for example, methacrylate esters, suchas C₁ to C₁₈ normal or branched alkyl esters of methacrylic acid,including methyl methacrylate, ethyl methacrylate, butyl methacrylate,2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate,or stearyl methacrylate; hydroxyalkyl methacrylates such as hydroxyethylmethacrylate; glycidylmethacrylate; phenyl methacrylate; methacrylamide;methacrylonitrile; or combinations thereof.

One skilled in the art will recognize that there are many ways toprepare the macromonomer useful in the present invention. For example,the macromonomer may be prepared by a high temperature (e.g., at least150° C.) continuous process such as disclosed in U.S. Pat. No. 5,710,227or EP-A-1,010,706, published Jun. 21, 2000. In a preferred continuousprocess, a reaction mixture of first ethylenically unsaturated monomersis passed through a heated zone having a temperature of at least 150°C., and more preferably at least 275° C. The heated zone may also bemaintained at a pressure above atmospheric pressure (e.g., greater than3,000 kPa=greater than 30 bar). The reaction mixture of monomers mayalso optionally contain a solvent such as water, acetone, methanol,isopropanol, propionic acid, acetic acid, dimethylformamide,dimethylsulfoxide, methylethylketone, or combinations thereof.

The macromonomer useful in the present invention may also be prepared bypolymerizing first ethylenically unsaturated monomers in the presence ofa free radical initiator and a catalytic metal chelate chain transferagent (e.g., a transition metal chelate). Such a polymerization may becarried out by a solution, bulk, suspension, or emulsion polymerizationprocess. Suitable methods for preparing the macromonomer using acatalytic metal chelate chain transfer agent are disclosed in forexample U.S. Pat. Nos. 4,526,945, 4,680,354, 4,886,861, 5,028,677,5,362,826, 5,721,330, and 5,756,605; European publicationsEP-A-0199,436, and EP-A-0196783; and PCT publications WO 87/03605, WO96/15158, and WO 97/34934.

Preferably, the macromonomer useful in the present invention is preparedby an aqueous emulsion free radical polymerization process using atransition metal chelate complex. Preferably, the transition metalchelate complex is a cobalt (II) or (III) chelate complex such as, forexample, dioxime complexes of cobalt (II), cobalt (II) porphyrincomplexes, or cobalt (II) chelates of vicinal iminohydroxyiminocompounds, dihydroxyimino compounds,diazadihydroxyiminodialkyldecadienes, ordiazadihydroxyiminodialkylundecadienes, or combinations thereof. Thesecomplexes may optionally include bridging groups such as BF₂, and mayalso be optionally coordinated with ligands such as water, alcohols,ketones, and nitrogen bases such as pyridine. Additional suitabletransition metal complexes are disclosed in for example U.S. Pat. Nos.4,694,054; 5,770,665; 5,962,609; and 5,602,220. A preferred cobaltchelate complex useful in the present invention is Co II(2,3-dioxyiminobutane-BF₂)₂, the Co III analogue of the aforementionedcompound, or combinations thereof. The spatial arrangements of suchcomplexes are disclosed in for example EP-A-199436 and U.S. Pat. No.5,756,605.

In preparing macromonomer by an aqueous emulsion polymerization processusing a transition metal chelate chain transfer agent, at least onefirst ethylenically unsaturated monomer is polymerized in the presenceof a free radical initiator and the transition metal chelate accordingto conventional aqueous emulsion polymerization techniques. Preferably,the first ethylenically unsaturated monomer is an α-methyl vinyl monomeras previously described herein.

The polymerization to form the macromonomer is preferably conducted at atemperature of from 20° C. to 150° C., and more preferably from 40° C.to 95° C. The solids level at the completion of the polymerization istypically from 5 weight percent to 70 weight percent, and morepreferably from 30 weight percent to 60 weight percent, based on thetotal weight of the aqueous emulsion.

The concentration of initiator and transition metal chelate chaintransfer agent used during the polymerization process is preferablychosen to obtain the desired degree of polymerization of themacromonomer. Preferably, the concentration of initiator is from 0.2weight percent to 3 weight percent, and more preferably from 0.5 weightpercent to 1.5 weight percent, based on the total weight of monomer.Preferably, the concentration of transition metal chelate chain transferagent is from 5 ppm to 200 ppm, and more preferably from 10 ppm to 100ppm, based on the total monomers used to form the macromonomer.

The first ethylenically unsaturated monomer, initiator, and transitionmetal chelate chain transfer agent may be added in any manner known tothose skilled in the art to carry out the polymerization. For example,the monomer, initiator and transition metal chelate may all be presentin the aqueous emulsion at the start of the polymerization process(i.e., a batch process). Alternatively, one or more of the componentsmay be gradually fed to an aqueous solution (i.e., a continuous orsemi-batch process). For example, it may be desired to gradually feedthe entire or a portion of the initiator, monomer, and/or transitionmetal chelate to a solution containing water and surfactant. In apreferred embodiment, at least a portion of the monomer and transitionmetal chelate are gradually fed during the polymerization, with theremainder of the monomer and transition metal chelate being present inthe aqueous emulsion at the start of the polymerization. In thisembodiment, the monomer may be fed as is, or suspended or emulsified inan aqueous solution prior to being fed.

Any suitable free radical initiator may be used to prepare themacromonomer. The initiator is preferably selected based on suchparameters as its solubility in one or more of the other components(e.g., monomers, water); half life at the desired polymerizationtemperature (preferably a half life within the range of from about 30minutes to about 10 hours), and stability in the presence of thetransition metal chelate. Suitable initiators include for example azocompounds such as 2,2′-azobis (isobutyronitrile),4,4′-azobis(4-cyanovaleric acid), 2,2′-azobis[2-methyl-N-(1,1-bis(hydroxymethyl)-2-(hydroxyethyl)]-propionamide, and2,2′-azobis [2-methyl-N-(2-hydroxyethyl)]-propionamide; peroxides suchas t-butyl hydroperoxide, benzoyl peroxide; sodium, potassium, orammonium persulphate or combinations thereof. Redox initiator systemsmay also be used, such as for example persulphate or peroxide incombination with a reducing agent such as sodium metabisulphite, sodiumbisulfite, sodium formaldehyde sulfoxylate, isoascorbic acid, orcombinations thereof. Metal promoters, such as iron, may also optionallybe used in such redox initiator systems. Also, buffers, such as sodiumbicarbonate may be used as part of the initiator system.

An emulsifier is also preferably present during the aqueous emulsionpolymerization process to prepare the macromonomer. Any emulsifier maybe used that is effective in emulsifying the monomers such as forexample anionic, cationic, or nonionic emulsifiers. In a preferredembodiment, the emulsifier is anionic such as for example sodium,potassium, or ammonium salts of dialkylsulphosuccinates; sodium,potassium, or ammonium salts of sulphated oils; sodium, potassium, orammonium salts of alkyl sulphonic acids, such as sodium dodecyl benzenesulfonate; sodium, potassium, or ammonium salts of alkyl sulphates, suchas sodium lauryl sulfate; ethoxylated alkyl ether sulfates; alkali metalsalts of sulphonic acids; C12 to C24 fatty alcohols, ethoxylated fattyacids or fatty amides; sodium, potassium, or ammonium salts of fattyacids, such as Na stearate and Na oleate; or combinations thereof. Theamount of emulsifier in the aqueous emulsion is preferably from 0.05weight percent to 10 weight percent, and more preferably from 0.3 weightpercent to 3 weight percent, based on the total weight of the monomers.

The macromonomer thus prepared is emulsion polymerized with at least onesecond ethylenically unsaturated monomer to form a copolymer compositioncontaining graft copolymer particles. The polymerization is carried outby providing the macromonomer as water insoluble particles in amacromonomer aqueous emulsion and the second ethylenically unsaturatedmonomer in a monomer composition. At least a portion of the macromonomeraqueous emulsion is combined with at least a portion of the monomercomposition to form a polymerization reaction mixture that ispolymerized in the presence of an initiator.

Although in no way intending to be bound by theory, it is believed that,by providing the macromonomer in the form of water insolublemacromonomer particles in an aqueous emulsion and providing the secondethylenically unsaturated monomer in a separate monomer composition,upon combination the second ethylenically unsaturated monomer diffusesthrough the aqueous phase and then into the macromonomer particles wherethe polymerization occurs. Preferably, the diffusion of the secondethylenically unsaturated monomer into the macromonomer particles isevidenced by swelling of the macromonomer particles. Prior to beingcombined with the monomer composition, the macromonomers are present inplural discrete particles dispersed in the aqueous phase. Preferably,these plural macromonomer particles have previously been formed byaqueous emulsion polymerization, and the resultant macromonomer aqueousemulsion is combined with the monomer composition and subsequentlypolymerized without being isolated. Addition of the monomer compositionto the macromonomer aqueous emulsion results initially in the presenceof plural monomer droplets in the aqueous emulsion as separate entitiesdistributed among, but not in direct contact with, the pluralmacromonomer particles. That is, the monomer droplets are separated fromthe macromonomer particles, and from each other, by an aqueous phase.Individual monomer molecules must then exit the monomer droplet,dissolve in the aqueous phase, diffuse through that aqueous phase to amacromonomer particle, and enter that macromonomer particle wherepolymerization to form the graft copolymer (preferably, comb copolymer)occurs. Because the water insoluble macromonomers are unable to diffusethrough the aqueous phase, it is essential that the monomer droplets notinclude water insoluble macromonomer if gel formation is to be avoidedand if the number of particles initially established by the macromonomerparticles is to be maintained during polymerization of monomers withmacromonomers.

The macromonomer aqueous emulsion useful in the present invention may beformed in any manner known to those skilled in the art. For example, themacromonomer, produced by any known method, may be isolated as a solid(e.g., spray dried) and emulsified in water. Also, for example, themacromonomer, if prepared via an emulsion or aqueous basedpolymerization process, may be used as is, or diluted with water orconcentrated to a desired solids level.

In a preferred embodiment of the present invention, the macromonomeraqueous emulsion is formed from the emulsion polymerization of at leastone first ethylenically unsaturated monomer in the presence of atransition metal chelate chain transfer agent as described previouslyherein. This embodiment is preferred for numerous reasons. For example,the macromonomer polymerization can be readily controlled to produce adesired particle size distribution (preferably narrow, e.g.,polydispersity less than 2). Also, for example, additional processingsteps, such as isolating the macromonomer as a solid, can be avoided,leading to better process economics. In addition, the macromonomer,macromonomer aqueous emulsion, and the graft copolymer can be preparedby consecutive steps in a single reactor which is desirable in acommercial manufacturing facility because process parameters, such asmanufacturing cost and particle size distribution, may be optimized.

The “macromonomer aqueous emulsion” useful in the present inventioncontains from 20 weight percent to 60 weight percent, and morepreferably from 30 weight percent to 50 weight percent of at least onewater insoluble macromonomer, based on the total weight of macromonomeraqueous emulsion. The macromonomer aqueous emulsion may also containmixtures of macromonomer. Preferably, the macromonomer aqueous emulsioncontains less than 5 weight percent and more preferably less than 1weight percent of ethylenically unsaturated monomer, based on the totalweight of macromonomer aqueous emulsion.

The water insoluble macromonomer particles have a particle size chosensuch that, upon addition of monomers, particles of graft copolymerhaving a desired particle size will be formed. For example, the finalgraft copolymer particle size is directly proportional to the initialparticle size of the macromonomer and the concentration of secondethylenically unsaturated monomer in the polymerization reactionmixture, assuming all the particles participate equally in thepolymerization. Preferably, the macromonomer particles have a weightaverage particle size of from 50 nm to 500 nm, and more preferably from80 nm to 200 nm as measured by Capillary Hydrodynamic Fractionationtechnique using a Matec CHDF 2000 particle size analyzer equipped with aHPLC type Ultra-violet detector.

The macromonomer aqueous emulsion may also include one or moreemulsifying agents. The type and amount of emulsifying agent ispreferably selected in a manner to produce the desired particle size.Suitable emulsifying agents include those previously disclosed for usein preparing the macromonomer by an emulsion polymerization process.Preferred emulsifying agents are anionic surfactants such as, forexample, sodium lauryl sulfate, sodium dodecylbenzene sulfonate,sulfated and ethoxylated derivatives of nonylphenols and fatty alcohols.The total level of emulsifying agent, based on the total weight ofmacromonomer is preferably from 0.2 weight percent to 5 weight percentand more preferably from 0.5 weight percent to 2 weight percent.

The “monomer composition” useful in the present invention contains atleast one kind of ethylenically unsaturated monomer. The monomercomposition may contain all (i.e., 100%) monomer, or contain monomerdissolved or dispersed in an organic solvent and/or water. Preferably,the level of monomer in the monomer composition is from 50 weightpercent to 100 weight percent, more preferably from 60 to 90 weightpercent, and most preferably from 70 to 80 weight percent, based on thetotal weight of the monomer composition. Examples of organic solventsthat may be present in the monomer composition include C₆ to C₁₄alkanes. The organic solvent in the monomer composition will be no morethan 30 weight percent, and more preferably no more than 5 weightpercent, based on the total weight of the monomer composition.

In addition to water and/or organic solvent, the monomer composition mayalso optionally contain monomers containing functional groups, such as,for example, monomers containing hydroxy, amido, aldehyde, ureido,polyether, glycidylalkyl, keto groups or combinations thereof. Theseother monomers are generally present in the monomer composition at alevel of from 0.5 weight percent to 15 weight percent, and morepreferably from 1 weight percent to 3 weight percent based on the totalweight of the graft copolymer. Examples of functional monomers includeketofunctional monomers such as the acetoacetoxy esters of hydroxyalkylacrylates and methacrylates (e.g., acetoacetoxyethyl methacrylate) andketo-containing amides (e.g., diacetone acrylamide); allyl alkylmethacrylates or acrylates; glycidylalkyl methacrylates or acrylates; orcombinations thereof. Such functional monomer can provide crosslinkingif desired.

In a preferred embodiment, the monomers in the monomer composition arepre-emulsified in water to form a “monomer aqueous emulsion”.Preferably, the monomer aqueous emulsion contains monomer dropletshaving a droplet size from 0.05 micron to 100 microns, more preferablyfrom 1 micron to 100 microns, and most preferably from 5 microns to 50microns. Any suitable emulsifying agent may be used, for example thosepreviously described, to emulsify the monomer to the desired monomerdroplet size. Preferably, the level of emulsifying agent, if present,will be from 0.2 weight percent to 2 weight percent based on the totalweight of monomer in the monomer composition.

The ethylenically unsaturated monomer of the monomer composition ispreferably selected to provide the desired properties in the resultingcopolymer (e.g., graft copolymer) composition. Suitable ethylenicallyunsaturated monomers include for example methacrylate esters, such as C₁to C₁₈ normal or branched alkyl esters of methacrylic acid, includingmethyl methacrylate, ethyl methacrylate, n-butyl methacrylate,2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate,isobornyl methacrylate; acrylate esters, such as C₁ to C₁₈ normal orbranched alkyl esters of acrylic acid, including methyl acrylate, ethylacrylate, n-butyl acrylate and 2-ethylhexyl acrylate; styrene;substituted styrenes, such as methyl styrene, a-methyl styrene ort-butyl styrene; olefinically unsaturated nitriles, such asacrylonitrile or methacrylonitrile; olefinically unsaturated halides,such as vinyl chloride, vinylidene chloride or vinyl fluoride; vinylesters of organic acids, such as vinyl acetate; N-vinyl compounds suchas N-vinyl pyrrolidone; acrylamide; methacrylamide; substitutedacrylamides; substituted methacrylamides; hydroxyalkylmethacrylates suchas hydroxyethylmethacrylate; hydroxyalkylacrylates; dienes such as1,3-butadiene and isoprene; vinyl ethers; or combinations thereof. Theethylenically unsaturated monomer can also be an acid containing monomeror a functional monomer, such as those previously described herein.Preferably, the ethylenically unsaturated monomer of the monomercomposition does not contain amino groups.

In a preferred embodiment, the monomer composition includes one or moreethylenically unsaturated monomers selected from C₁ to C₁₈ normal orbranched alkyl esters of acrylic acid, including methyl acrylate, ethylacrylate, n-butyl acrylate and 2-ethylhexyl acrylate; styrene;substituted styrenes, such as methyl styrene, (α-methyl styrene ort-butyl styrene; butadiene or combinations thereof.

As previously mentioned, the macromonomer aqueous emulsion and monomercomposition are combined to form a “polymerization reaction mixture”,and polymerized in the presence of a free radical initiator to form an“aqueous copolymer composition”, also referred to herein as an “aqueousdispersion of a segmental copolymer”. The term “polymerization reactionmixture,” as used herein, refers to the resulting mixture formed when atleast a portion of the macromonomer aqueous emulsion and at least aportion of the monomer composition are combined. The polymerizationreaction mixture may also contain initiator or any other additive usedduring the polymerization. Thus, the polymerization reaction mixture isa mixture that changes in composition as the macromonomer and monomer inthe monomer composition are reacted to form graft copolymer.

The macromonomer aqueous emulsion and monomer composition may becombined in various ways to carry out the polymerization. For example,the macromonomer aqueous emulsion and the monomer composition may becombined prior to the start of the polymerization reaction to form thepolymerization reaction mixture. Alternatively, the monomer compositioncould be gradually fed into the macromonomer aqueous emulsion, or themacromonomer aqueous emulsion could be gradually fed into the monomercomposition. It is also possible that only a portion of the macromonomeraqueous emulsion and/or monomer composition be combined prior to thestart of the polymerization with the remaining monomer compositionand/or macromonomer aqueous emulsion being fed during thepolymerization.

The initiator can also be added in various ways. For example, theinitiator may be added in “one shot” to the macromonomer aqueousemulsion, the monomer composition, or a mixture of the macromonomeraqueous emulsion and the monomer composition at the start of thepolymerization. Alternatively, all or a portion of the initiator can beco-fed as a separate feed stream, as part of the macromonomer aqueousemulsion, as part of the monomer composition, or any combination ofthese methods.

The preferred method of combining the macromonomer aqueous emulsion, themonomer composition, and initiator will depend on such factors as thedesired graft copolymer composition. For example, the distribution ofthe macromonomer as a graft along the backbone can be affected by theconcentrations of both the macromonomer and the second ethylenicallyunsaturated monomers at the time of the polymerization. In this regard,a batch process will afford high concentration of both the macromonomerand the second ethylenically unsaturated monomers at the onset of thepolymerization whereas a semi-continuous process will keep the secondethylenically unsaturated monomer concentration low during thepolymerization. Thus, through the method by which the macromonomeraqueous emulsion and monomer composition are combined, it is possible tocontrol, for example: the number of graft segments, derived frommacromonomer, per polymer chain; the distribution of graft segments ineach chain, and the length of the polymer backbone.

Initiators useful in polymerizing the macromonomer and secondethylenically unsaturated monomer include any suitable initiator foremulsion polymerizations known to those skilled in the art. Theselection of the initiator will depend on such factors as theinitiator's solubility in one or more of the reaction components (e.g.monomer, macromonomer, water); and half life at the desiredpolymerization temperature (preferably a half life within the range offrom about 30 minutes to about 10 hours). Suitable initiators includethose previously described herein in connection with forming themacromonomer, such as azo compounds such as 4,4′-azobis(4-cyanovalericacid), peroxides such as t-butyl hydroperoxide; sodium, potassium, orammonium persulfate; redox initiator systems such as, for example,persulphate or peroxide in combination with a reducing agent such assodium metabisulfite, sodium bisulfite, sodium formaldehyde sulfoxylate,isoascorbic acid; or combinations thereof. Metal promoters, such asiron; and buffers, such as sodium bicarbonate, may also be used incombination with the initiator. Additionally, Controlled Free RadicalPolymerization (CFRP) methods such as Atom Transfer RadicalPolymerization; or Nitroxide Mediated Radical Polymerization may beused. Preferred initiators include azo compounds such as4,4′-azobis(4-cyanovaleric acid).

The amount of initiator used will depend on such factors as thecopolymer desired and the initiator selected. Preferably, from 0.1weight percent to 1 weight percent initiator is used, based on the totalweight of monomer and macromonomer.

The polymerization temperature will depend on the type of initiatorchosen and desired polymerization rates. Preferably, however, themacromonomer and second ethylenically unsaturated monomer arepolymerized at a temperature of from 0° C. to 150° C., and morepreferably from 20° C. to 95° C.

The amount of macromonomer aqueous emulsion and monomer compositionadded to form the polymerization reaction mixture will depend on suchfactors as the concentrations of macromonomer and second ethylenicallyunsaturated monomer in the macromonomer aqueous emulsion and monomercomposition, respectively, and the desired graft copolymer composition.Preferably, the macromonomer aqueous emulsion and monomer compositionare added in amounts to provide a graft copolymer containing aspolymerized units from 2 weight percent to 90 weight percent, morepreferably from 5 weight percent to 50 weight percent, and mostpreferably from 5 weight percent to 45 weight percent macromonomer, andfrom 10 weight percent to 98 weight percent, more preferably from 50weight percent to 95 weight percent and most preferably from 55 weightpercent to 95 weight percent second ethylenically unsaturated monomer.

One skilled in the art will recognize that other components used inconventional emulsion polymerizations may optionally be used in themethod of the present invention. For example, to reduce the molecularweight of the resulting graft copolymer, the polymerization mayoptionally be conducted in the presence of one or more chain transferagents, such as n-dodecyl mercaptan, thiophenol; halogen compounds suchas bromotrichloromethane; or combinations thereof. Also, additionalinitiator and/or catalyst may be added to the polymerization reactionmixture at the completion of the polymerization reaction to reduce anyresidual monomer, (e.g., chasing agents). Suitable initiators orcatalysts include those initiators previously described herein. Inaddition, the chain transfer capacity of a macromonomer throughaddition-fragmentation can be utilized in part to reduce molecularweight through appropriate design of monomer compositions andpolymerization conditions. See e.g., E. Rizzardo, et. al., Prog. PacificPolym. Sci., 1991, 1, 77-88; G. Moad, et. al., WO 96/15157.

Preferably, the process of the present invention does not requireneutralization of the monomer, or resulting aqueous graft copolymercomposition. These components preferably remain in unneutralized form(e.g., no neutralization with a base if acid functional groups arepresent).

The resulting aqueous comb copolymer composition formed bypolymerization of the macromonomer and the ethylenically unsaturatedmonomer in the monomer composition preferably has a solids level of from30 weight percent to 70 weight percent and more preferably from 40weight percent to 60 weight percent. The aqueous comb copolymercomposition contains comb copolymer particles preferably having a weightaverage particle size of from 50 nm to 1,000 nm, more preferably from 60nm to 500 nm, and most preferably from 80 nm to 200 nm.

The graft copolymer formed preferably has a backbone containing, aspolymerized units, the second ethylenically unsaturated monomer from themonomer composition, and one or more macromonomer units, as polymerizedunits, wherein a terminal ethylenically unsaturated group of themacromonomer is incorporated into the backbone and the remainder of themacromonomer becomes a graft segment pendant to the backbone (i.e., aside chain) upon polymerization. Preferably, each side chain is a graftsegment derived from the grafting of one macromonomer to the backbone.

The degree of polymerization of the graft segments derived from themacromonomer is preferably from 5 to 1,000, preferably from 10 to 1,000,more preferably 10 to 200, and most preferably from 20 to less than 50,where the degree of polymerization is expressed as the number ofpolymerized units of ethylenically unsaturated monomer used to form themacromonomer. The weight average molecular weight of the graft copolymer(e.g., of the comb copolymer) is preferably in the range of from 50,000to 2,000,000, and more preferably from 100,000 to 1,000,000. Weightaverage molecular weights as used herein can be determined by sizeexclusion chromatography.

The graft copolymer particles of the aqueous graft copolymer compositioncan be isolated, for example, by spray drying or coagulation, followedby forming a coating by powder coating methods, or by redispersing in anaqueous medium. However, it is preferable to use the aqueous copolymercomposition (i.e., the aqueous dispersion of segmental copolymer)without an intermediate isolation step to form a film.

In a preferred embodiment of the present invention, the polymerizationis conducted in two stages. In the first stage, the macromonomer isformed in an aqueous emulsion polymerization process, and in the secondstage the macromonomer is polymerized with the second ethylenicallyunsaturated monomer in an emulsion. For efficiency, preferably these twostages are conducted in a single vessel. For example, in the firststage, the macromonomer aqueous emulsion may be formed by polymerizingin an aqueous emulsion at least one first ethylenically unsaturatedmonomer to form water insoluble macromonomer particles. This first stagepolymerization is preferably conducted using a transition metal chelatechain transfer agent as previously described herein. After forming themacromonomer aqueous emulsion, a second emulsion polymerization ispreferably performed in the same vessel to polymerize the macromonomerwith at least one second ethylenically unsaturated monomer. This secondstage may be conducted for example by directly adding (e.g., all at onceor by a gradual feed) the monomer composition and initiator to themacromonomer aqueous emulsion. One main advantage of this embodiment isthat the macromonomer does not have to be isolated, and the secondpolymerization can take place simply by adding the monomer compositionand initiator to the macromonomer aqueous emulsion. In this preferredembodiment, the particle size and particle size distribution of theplural water insoluble macromonomer particles may be preciselycontrolled, and later addition of more macromonomer aqueous emulsionwould typically not be required, except when, for example, a second mode(particle size and/or composition) of graft copolymer is desired.

In another preferred embodiment of the present invention, thepolymerization of the macromonomer and second ethylenically unsaturatedmonomer is at least partially performed in the presence of an acidcontaining monomer, acid containing macromonomer, or combinationsthereof. The acid containing monomer or acid containing macromonomer maybe added in any manner to the polymerization reaction mixture.Preferably, the acid containing monomer or acid containing macromonomeris present in the monomer composition. The acid containing monomer oracid containing macromonomer may also be added as a separate stream tothe polymerization reaction mixture.

The amount of acid containing monomer or acid containing macromonomeradded to the polymerization reaction mixture is preferably from 0.2weight percent to 10 weight percent, more preferably from 0.5 weightpercent to 5 weight percent, and most preferably from 1 weight percentto 2 weight percent, based on the total weight of monomer andmacromonomer added to the polymerization reaction mixture.

Acid containing monomers which may be used in this embodiment includeethylenically unsaturated monomers bearing acid functional or acidforming groups such as those previously described herein. The “acidcontaining macromonomer” useful in this embodiment is any low molecularweight polymer having at least one terminal ethylenically unsaturatedgroup that is capable of being polymerized in a free radicalpolymerization process, and that is formed from at least one kind ofacid containing monomer. Preferably, the amount of acid containingmonomer present, as polymerized units, in the acid containingmacromonomer is from 50 weight percent to 100 weight percent, morepreferably from 90 weight percent to 100 weight percent, and mostpreferably from 95 weight percent to 100 weight percent.

The acid containing macromonomer may be prepared according to anytechnique known to those skilled in the art such as those previouslydescribed herein. In a preferred embodiment of the present invention,the acid containing macromonomer is prepared by a solutionpolymerization process using a free radical initiator and transitionmetal chelate complex. Such a process is disclosed in, for example, U.S.Pat. No. 5,721,330. Preferred acid containing monomers used to form theacid containing macromonomer are α-methyl vinyl monomers such asmethacrylic acid.

In another preferred embodiment of the present invention, a“macromolecular organic compound” having a hydrophobic cavity is presentin the polymerization medium used to form the macromonomer and/oraqueous copolymer composition. Although the macromolecular organiccompound may be used to facilitate transport of any ethylenicallyunsaturated monomer through the aqueous phase of the polymerizationreaction mixture, preferably, the macromolecular organic compound isused when copolymerizing ethylenically unsaturated monomers with a watersolubility of no greater than 150 millimoles/liter, more preferably nogreater than 50 millimoles/liter. Herein, a water solubility at 25° C.to 50° C. of no greater than 50 millimoles/liter is referred to as “verylow water solubility”. Ethylenically unsaturated monomers having verylow water solubility include, for example, lauryl (meth)acrylate andstearyl (meth)acrylate. The macromolecular organic compound may, forexample, be added to the monomer composition, the macromonomer aqueousemulsion, or the polymerization reaction mixture used to form theaqueous copolymer composition. Also, for example, the macromolecularorganic compound may be added to an aqueous emulsion of ethylenicallyunsaturated monomer used to form the macromonomer. Suitable techniquesfor using a macromolecular organic compound having a hydrophobic cavityare disclosed in, for example, U.S. Pat. No. 5,521,266.

Preferably, the macromolecular organic compound having a hydrophobiccavity is added to the polymerization reaction mixture to provide amolar ratio of macromolecular organic compound to very low watersolubility monomer or macromonomer of from 5:1 to 1:5000 and morepreferably from 1:1 to 1:500.

Macromolecular organic compounds having a hydrophobic cavity useful inthe present invention include for example cyclodextrin or cyclodextrinderivatives; cyclic oligosaccharides having a hydrophobic cavity such ascycloinulohexose, cycloinuloheptose, or cycloinuloctose; calyxarenes;cavitands; or combinations thereof. Preferably, the macromolecularorganic compound is β-cyclodextrin, more preferablymethyl-β-cyclodextrin.

Monomers having low water solubility include for example primaryalkenes; styrene and alkylsubstituted styrene; α-methyl styrene;vinyltoluene; vinyl esters of C₄ to C₃₀ carboxylic acids, such as vinyl2-ethylhexanoate, vinyl neodecanoate; vinyl chloride; vinylidenechloride; N-alkyl substituted (meth)acrylamide such as octyl acrylamideand maleic acid amide; vinyl alkyl or aryl ethers with (C₃-C₃₀) alkylgroups such as stearyl vinyl ether; (C₁-C₃₀) alkyl esters of(meth)acrylic acid, such as methyl methacrylate, ethyl (meth)acrylate,butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl(meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl(meth)acrylate, stearyl (meth)acrylate; unsaturated vinyl esters of(meth)acrylic acid such as those derived from fatty acids and fattyalcohols; multifunctional monomers such as pentaerythritol triacrylate;monomers derived from cholesterol or combinations thereof.

In another aspect of the present invention an “aqueous copolymercomposition” is provided that is preferably produced by the method ofthe present invention as previously described herein. The aqueouscopolymer composition contains a plurality of water insoluble particlesof graft copolymer that are preferably comb copolymer particles. Thecomb copolymer particles preferably have a weight average particle sizeof from 50 nm to 1,000 nm, more preferably from 60 nm to 500 nm, andmost preferably from 80 nm to 200 nm.

Preferably, the particles of graft copolymer contain from 2 weightpercent to 90 weight percent, and more preferably from 5 weight percentto 50 weight percent polymerized units of a macromonomer, based on thetotal weight of the copolymer, where the macromonomer preferably has acomposition as previously described herein for the water insolublemacromonomer present in the macromonomer aqueous emulsion. The graftcopolymer particles also preferably contain from 10 weight percent to 98weight percent, and more preferably from 50 weight percent to 95 weightpercent polymerized units of at least one second ethylenicallyunsaturated monomer, based on the total weight of the copolymer. Theethylenically unsaturated monomer may be any ethylenically unsaturatedmonomer that provides desirable properties in the copolymer particles,such as those useful in the monomer composition as previously describedherein.

Preferably, the backbone of the graft copolymer is linear.Compositionally, the backbone of the copolymer preferably containspolymerized units of the scond ethylenically unsaturated monomer derivedfrom the monomer composition. Preferably, the backbone contains lessthan 20 mole percent, and more preferably less than 10 mole percent ofpolymerized macromonomer derived from the macromonomer aqueous emulsion,based on the total moles of monomer, as polymerized units, in thecopolymer. Preferably, the Tg of the backbone is from −90° C. to 50° C.,more preferably −80° C. to 25° C., and most preferably −60° C. to 0° C.The pendant graft segments of the graft copolymer preferably containpolymerized units of the macromonomer. The carbon atoms of the doublebond of the macromonomer, and other atoms such a hydrogen and groupssuch as methyl directly attached to those carbon atoms, become, as apolymerized unit, part of the backbone of the graft copolymer, while theremainder of the macromonomer becomes a graft segment of the graftcopolymer. In a preferred embodiment of the present invention, eachgraft segment is derived from one macromonomer. The graft segmentcontains as polymerized units less than 10 weight percent, preferablyless than 5 weight percent, more preferably less than 2 weight percentand most preferably less than 1 weight percent acid containing monomer,based on the weight of the macromonomer from which it was derived. In amost preferred embodiment, the graft segment contains no acid containingmonomer. Further, the graft segment may be free of non-methacrylatemonomer, but typically contains, as polymerized units, at least onemolecule of non-methacrylate monomer, preferably 5 weight percent to 50weight percent non-methacrylate monomer, more preferably 10 weightpercent to 35 weight percent non-methacrylate monomer, and mostpreferably 15 weight percent to 25 weight percent of non-methacrylatemonomer, based on the weight of the macromonomer from which it wasderived. Additionally, the pendant graft segments contain less than 5weight percent and more preferably less than 1 weight percent of thepolymerized second ethylenically unsaturated monomer derived from themonomer composition, based on the total weight of the pendant graftsegments.

Preferably, the Tg of the graft segment is from 30° C. to 130° C., morepreferably from 40° C. to 120° C., and most preferably from 50° C. to105° C.

Preferably, the graft segment is present in the graft copolymer at from1 weight percent to 70 weight percent, more preferably 2 to 45 weightpercent, and most preferably 5 to 35 weight percent, based on the weightof the comb copolymer, where the weight of the graft segment is taken asthe weight of the macromonomer from which the graft segment was derived.

Preferably, the overall weight average molecular weight of the graftcopolymer is from 50,000 to 2,000,000, and more preferably from 100,000to 1,000,000.

In a preferred embodiment of the present invention, the water insolublegraft copolymer particles further contain from 0.2 weight percent to 10weight percent, more preferably from 0.5 weight percent to 5 weightpercent, and most preferably from 1 weight percent to 2 weight percentof an acid containing macromonomer, based on the total weight of thegraft copolymer. The acid containing macromonomer preferably has acomposition as previously described herein.

Although in no way intending to be bound by theory, it is believed thatthe “acid containing macromonomer” is attached to the surface of thewater insoluble graft copolymer particles and provides stability. By“attached,” as used herein, it is believed that the acid containingmacromonomer is bound in some manner (e.g., covalent, hydrogen bonding,ionic) to a polymer chain in the particle. Preferably, the acidcontaining macromonomer is covalently bound to a polymer chain in theparticle. The acid containing macromonomer is most effective whenpresent at the surface of the graft copolymer particle. As such, it isnot necessary that even one acid containing macromonomer unit beincorporated into every graft compolymer. In fact, it is preferablethat, when units of acid containing macromonomer are attached to chainsof graft copolymer, those chains are at the surface of the graftcopolymer particles. It has been found that the acid containingmacromonomer provides stability to the particles such that the aqueouscopolymer composition produced exhibits unexpected improved shearstability; freeze thaw stability; and stability to additives informulations, as well as reduction of coagulum during thepolymerization. Although improved stability can be achieved using acidcontaining monomer, these benefits are most dramatic when an acidcontaining macromonomer is used.

The aqueous copolymer composition in addition to the copolymer particlespreferably contains less than 10 weight percent, and more preferablyless than 1 weight percent of organic solvent, based on the weight ofcopolymer particles. In a most preferred embodiment, the aqueouscopolymer composition contains no organic solvent.

An advantage of using the method of the present invention to prepare theaqueous copolymer composition is that the resulting copolymercomposition contains low levels of homopolymer, such as for examplehomopolymer of second ethylenically unsaturated monomer derived from themonomer composition or homopolymer of macromonomer derived from themacromonomer aqueous emulsion. Preferably the aqueous copolymercomposition contains less than 30 weight percent and more preferablyless than 20 weight percent of homopolymer of macromonomer, based on thetotal weight of the graft copolymer. Preferably also the aqueouscopolymer composition contains less than 30 weight percent and morepreferably less than 20 weight percent of homopolymer of ethylenicallyunsaturated monomer.

The aqueous dispersion of the present invention may include acoalescent. The coalescent of the present invention may be anycoalescent known to the art. For example, many common solvents are usein the art as coalescents. It is preferred that the coalescent ispresent in the amount of from 0 weight percent to 40 weight percent,more preferably 0 weight percent to 20 weight percent, and mostpreferably 0 weight percent to 5 weight percent, based on the weight ofthe comb copolymer. In a most preferred embodiment, the aqueous coatingcomposition contains no coalescent. The aqueous dispersion of thepresent invention may further contain an emulsion polymer not meetingthe limitations of the segmental copolymer of the present invention,including a film-forming and/or a non-film-forming emulsion polymer.This emulsion polymer may be introduced by blending or in-situpolymerization. When included in the aqueous dispersion, the emulsionpolymer not meeting the limitations of the comb copolymer of the presentinvention is preferably present in an amount of from 1 weight percent to99 weight percent, more preferably 5 weight percent to 95 weightpercent, and most preferably 10 weight percent to 90 weight percent,based on the combined weight of the comb copolymer and the emulsionpolymer not meeting the limitations of the comb copolymer of the presentinvention.

The aqueous copolymer compositions produced by the method of the presentinvention are useful in a variety of applications. For example, theaqueous copolymer compositions may be used in architectural andindustrial coatings including paints, wood coatings, or inks; papercoatings; textile and nonwoven binders and finishes; adhesives; mastics;asphalt additives; floor polishes; leather coatings; plastics; plasticadditives; petroleum additives; thermoplastic elastomers or combinationsthereof.

When the aqueous copolymer compositions of the present invention areused as coatings compositions, it is often desirable to have additionalcomponents added to the coating composition to form the finalformulation for coating compositions, including traffic paints,described herein. These additional components include, for example,thickeners; rheology modifiers; dyes; sequestering agents; biocides;dispersants; pigments, such as, titanium dioxide, organic pigments,carbon black; extenders, such as calcium carbonate, talc, clays, silicasand silicates; fillers, such as glass or polymeric microspheres, quartzand sand; anti-freeze agents; plasticizers; adhesion promoters such assilanes; coalescents; wetting agents; surfactants; slip additives;crosslinking agents; defoamers; colorants; tackifiers; waxes;preservatives; freeze/thaw protectors; corrosion inhibitors; andanti-flocculants. During application of the aqueous coating compositionof the present invention to the surface of a substrate, glass orpolymeric microspheres, quartz and sand may be added as part of the thatcoating composition or as a separate component applied to the surface ina separate step simultaneously with, before, or after the step ofapplication of the aqueous coating composition.

The aqueous copolymer compositions produced by the method of the presentinvention are useful in a variety of applications. For example, theaqueous copolymer compositions may be used in architectural andindustrial coatings including paints, wood coatings, or inks; papercoatings; textile and nonwoven binders and finishes; adhesives; mastics;floor polishes; leather coatings; plastics; plastic additives; petroleumadditives; thermoplastic elastomers or combinations thereof.

Experimental Section EXAMPLES

Some embodiments of the invention will now be described in detail in thefollowing Examples. The following abbreviations shown in Table 1 areused in the examples:

Table 1: Abbreviations

Abbreviation A-16-22 Polystep A-16-22, anionic surfactant, supplied as22% solids by Stepan Company, located in Northfield, Illinois. EA Ethylacrylate BA Butyl acrylate MMA Methyl methacrylate BMA Butylmethacrylate MAA Methacrylic acid CoBFCo(II)-(2,3-dioxyiminobutane-BF₂)₂ CVA 4,4-azobis(4-cyanovaleric acid)GC Gas chromatograph SEC Size exclusion chromatography HPLC Highperformance liquid chromatography Init. Initiator IR Infraredspectroscopy NaPS Sodium persulfate Na₂CO₃ Sodium bicarbonate Mn Numberaverage molecular weight Mw Weight average molecular weight MMMacromonomer PMAA-MM Poly-methacrylic acid macromonomer MM MacromonomerPMMA-MM Poly-methyl methacrylate macromonomer Wako VA-0442,2′-azobis[2-(2-imidazolin2-2yl)propane]dihydrochloride

In the Examples, monomer conversion was determined by GC analysis ofunreacted monomer using standard methods. Weight percent solids for themacromonomer and copolymers were determined by gravimetric analysis.Particle size of the macromonomer and copolymer compositions wereobtained using a Matec CHDF 2000 particle size analyzer equipped with aHPLC type ultra-violet detector.

GPC, Gel Permeation Chromatography, otherwise known as SEC, SizeExclusion Chromatography, separates the members of a distribution ofpolymer chains according to their hydrodynamic size in solution ratherthan their molar mass. The system is then calibrated with standards ofknown molecular weight and composition to correlate elution time withmolecular weight. The techniques of GPC are discussed in detail inModern Size Exclusion Chromatography, W. W. Yau, J. J Kirkland, D. D.Bly; Wiley-Interscience, 1979, and in A Guide to MaterialsCharacterization and Chemical Analysis, J. P. Sibilia; VCH, 1988,p.81-84.

Macromonomer was measured for number average molecular weight by SECusing a polystyrene standard from Polymer Laboratories (PS-1) having apeak average molecular weight ranging from 580 to 7,500,000 with narrowmolecular weight distribution. Conversions from polystyrene to PMMA weremade using Mark-Houwink constants. Copolymer compositions were evaluatedfor number average molecular weight and weight average molecular weightusing SEC as follow: the sample is dissolved in THF at a concentrationof approximately 0.1% weight sample per volume THF, followed byfiltration through a 0.45 μm PTFE (polytetrafluoroethylene) membranefilter. The analysis is performed by injecting 100 μl of the abovesolution onto 3 columns connected in sequence and held at 40° C. Thethree columns are: one each of PL Gel 5 100, PL Gel 5 1,000, and PL Gel5 10,000, all available from Polymer Labs, Amherst, Mass. The mobilephase used is THF flowing at 1 ml/min. Detection is carried out by theuse of ELSD (Evaporative Light Scattering Detector). The system wascalibrated with narrow polystyrene standards. PMMA-equivalent molecularweights for the sample are calculated via Mark-Houwink correction usingK=14.1×10⁻³ ml/g and ?=0.70 for the polystyrene standards andK=10.4×10⁻³ ml/g and ?=0.697 for the sample.

Examples 1.1 to 1.9

Preparation of Macromonomers by Emulsion Polymerization

“Macromonomer” (“MM”) was prepared by emulsion polymerization processesin Examples 1.1 to 1.6. The polymerization was conducted in a 5-liter,four neck round bottom reaction flask equipped with a mechanicalstirrer, temperature control device, condenser, monomer feed line and anitrogen inlet except for example 1.1 which was prepared in a 5 gallonreactor with similar attachments. The specific amounts of water,surfactant, monomers, chain transfer agent (CTA), and initiator used inExamples 1.1 to 1.6 are shown in Table 2. These ingredients were addedaccording to the following procedure. In a different flask from thereaction flask, a monomer solution was prepared by dissolving the chaintransfer agent in the monomer mixture consisting of all the monomerslisted in Table 2 under a nitrogen purge. Deionized water and surfactantwere introduced into the reaction flask at room temperature to form awater surfactant solution. The water surfactant solution was mixed andheated to 80° C. with stirring under a nitrogen purge. Upon reaching atemperature of 80° C., and upon complete dissolution of the surfactant,the initiator (CVA) was added to the water surfactant solution withstirring for 2 minute to permit the initiator to dissolve. Afterdissolution of the initiator, MMA (245 g for example 1.1 and 63 g forexamples 1.2 to 1.6, respectively) was introduced into the reactionflask and allowed to react for 10 minutes. At the end of 10 minutes, 20percent by weight of the monomer solution was added to the reactionflask with stirring. Following this initial charge, the remainingmonomer solution was fed over a period of 2 hours, with stirring, toform a reaction mixture. At the end of the feed period, the reactionmixture was maintained at 80° C. for an additional 2 hours. The reactionmixture was then cooled to room temperature and passed through a filtercloth to remove any coagulum.

Generally, the resulting macromonomer emulsion contained less than 5weight percent coagulum based on the total weight of macromonomer, andthe conversion of monomer was over 99 weight percent, based on the totalweight of monomer added. The Mn, weight percent solids and particle sizefor each macromonomer are reported in Table 2.

TABLE 2 Preparation of Macromonomers (MM) Part. H₂O Surf. MMA CTA Init.Size Wt % Ex. (g) (g)⁽³⁾ (g) BMA EA MAA g⁽¹⁾ g⁽²⁾ (nm) Mn Solids 1.19256 214  4,655   — — — 0.29 49 84 11210 34.0 1.2 2380   54.8 838 —  299.4   59.8 0.16 12.6 100   9470 33.0 1.3 2300 51   928.8 185.8 — —0.08 11.8 99 14050 33.2 1.4 2380   54.8 838 —   299.4   59.8 0.16 12.681 10410 33.4 1.5 2380 55 1,160   — — — 0.20 12.6 100   3770 32.7 1.62380 55 1,197   — — — 0.07 12.6 62  8010 33.7 1.7⁽⁴⁾ 2300 51 710 — 25040 0.16 12.6 90 10000 30 1.8⁽⁴⁾ 2300 51 730 — 250 20 0.16 12.6 90 1000030 1.9⁽⁴⁾ 2300 51 750 — 250 — 0.16 12.6 90 10000 30 ⁽¹⁾Chain TransferAgent (CoBF) ⁽²⁾CVA, supplied by Aldrich as a 75 weight percent aqueoussolution of initiator. ⁽³⁾A-16-22. ⁽⁴⁾The values listed for Examples1.7-1.9 are the values one would use in preparation of the correspondingmacromonomers.

Example 2

Preparation of PMAA-MM by Solution Polymerization

“MAA macromonomer” (“PMAA-MM”) was prepared by aqueous solutionpolymerization in a 2-liter baffled flange flask equipped with amechanical stirrer, condenser, temperature control device, initiatorfeed lines and a nitrogen inlet. The apparatus was purged with nitrogenfor 30 minutes after 0.018 g of CoBF was added. Deionized water, 1080 g,was charged to the flask and heated to 55° C. under a nitrogen purge. Amonomer mixture containing 510 ml of MAA and 0.01 g of CoBF was preparedseparately under nitrogen. When the deionized water reached atemperature of 55° C., 1.94 g of initiator (Wako VA-044) was added tothe reaction flask. Following the addition of the initiator, the monomermixture was added over a period of 60 minutes to the reaction flask withstirring. The temperature was then held at 55° C. for 2 hours followingcompletion of the monomer mixture feed. Upon cooling the reaction flaskto room temperature, the MAA-MM (Example 2.1) was isolated as driedpolymer by rotary evaporation. The number average molecular weight (Mn)of the MAA-MM was determined by proton nuclear magnetic resonance to be4030 based on the integration of the vinyl end group with respect to themethyl and methylene groups of the polymer chain.

Example 3

Preparation of Acrylic Graft Copolymers by Semi-Continuous EmulsionPolymerization

In Examples 3.1 to 3.9 and 3.13 to 3.15, graft copolymers were preparedby a semi-continuous emulsion polymerization process in a 5-liter roundbottom flask with four neck equipped with a mechanical stirrer,temperature control device, initiator feed lines and a nitrogen inlet.The specific amounts of Macromonomer (MM, as emulsion), water,surfactant, monomers, acid containing monomers, and initiator used inExamples 3.1 to 3.9 and 3.13 to 3.15 are shown in Table 3. Theseingredients were added according to the following procedure. A monomeremulsion of deionized water (H₂O #2 in Table 3), surfactant, andmonomers (as listed in Table 3) was prepared in a separate flask.Deionized water (H₂O #1 in Table 3), MM from the example indicated inTable 2 and 20% of the monomer emulsion were introduced into thereaction flask at room temperature to form a reaction mixture. Thereaction mixture was heated to 85° C. while stirring under a nitrogenpurge. Upon reaching 85° C., the initiator and buffer solutions wereintroduced into the reaction flask. The remaining monomer emulsion wasadded over a period of 30 minutes with the temperature maintained at 90°C. Upon completion of the feeds, the reaction mixture was maintained atthe reaction temperature for a period of 1 hours. The resultingcopolymer composition was analyzed for conversion and other properties(Table 5). The conversion of BA and styrene, determined by standard GCmethods, was greater than 99 weight percent based on the total weight ofmonomer charged.

TABLE 3 Preparation of Acrylic Graft Copolymers by Semi-ContinuousEmulsion Polymerization. MM⁽¹⁾ H₂O H₂O Surf.⁽²⁾ BA Sty. Acid Init.⁽³⁾Buffer⁽⁴⁾ Ex. Ex Amt. (g) #1 (g) #2 (g) (g) (g) (g) (g)⁽⁵⁾ (g) (g) 3.11.4  919 200 101 14.9   445.4 111 12.7 0.6 0.6 3.2 1.5  892 380 200 28.21059 — 25.2 1.2 1.2 3.3 1.5 1783 380 200 28.2 1059 — 25.2 1.2 1.2 3.41.1 1806 546 203 29.7 1115 — 26.5 1.2 1.2 3.5 1.3 1915 340 420 30.8 1156— 27.4 1.3 1.3 3.6 1.6  521 800 600 34 1554 — 20.5 1.2 1.2 3.7 1.1 2433100 420 30.8 1011 — 27.4 1.3 1.3 3.8 1.2 1462 400 300 29.7   809.5 43626.3 1.2 1.2 3.9 1.2 1051 400 500 29.7 895 482 26.3 1.2 1.2 3.10⁽⁶⁾ 1.71500 400 200 30   653.5 163 19.2 1.2 1.2 3.11⁽⁶⁾ 1.8 1500 400 200 30  653.5 163 19.2 1.2 1.2 3.12⁽⁶⁾ 1.9 1500 400 200 30   653.5 163 19.21.2 1.2 3.13 1.1  541 500 950 30.8 1627 — 27.6 1.3 1.3 3.14 1.1  1081000  750 30.8 1774 — 27.6 1.3 1.3 3.15 1.1 1081 525 800 30.8 1443 —27.4 1.3 1.3 ⁽¹⁾Macromonomer emulsion prepared by method of Example 1.⁽²⁾Ethoxylated C₆ to C₁₈ alkyl ether sulfate having from 1 to 40ethylene oxide groups per molecule (30% active in water). ⁽³⁾NaPSdissolved in 10 g of water. ⁽⁴⁾Sodium carbonate dissolved in 15 g ofwater. ⁽⁵⁾PMAA-MM (prepared by method of Example 2.1) ⁽⁶⁾The valueslisted for Examples 3.10-3.12 are the values one would use inpreparation of the corresponding acrylic graft copolymers (i.e., combcopolymer).

Example 4

Preparation of Comparative Examples

In Examples C-4.1 to C-4.6, random copolymers were prepared bysemi-continuous emulsion polymerization in a 5-liter round bottom flaskwith four neck equipped with a mechanical stirrer, temperature controldevice, initiator feed lines and a nitrogen inlet. The specific amountsof water, surfactant, monomers used in Examples C-4.1 to C-4.6 are shownin Table 4. These ingredients were added according to the followingprocedure. A monomer emulsion of deionized water (H₂O #2 in Table 4),surfactant (Surf. #2 in Table 4), and monomers (as listed in Table 4)was prepared in a separate flask. Deionized water (H₂O #1 in Table 4),and surfactant (Surf. #1, except for C-4.6) were introduced into thereaction flask at room temperature to form a reaction mixture. Thereaction mixture was heated to the 85° C. while stirring under anitrogen purge. Upon reaching 85° C., an initiator solution (5.3 g ofNaPS except for C-4.6 with 0.54 g, in 30 g of water) and a buffersolution (5.3 g of Na₂CO₃ except for C-4.6 with 1.21 g, in 30 g ofwater) were introduced into the reaction flask with stirring. Themonomer emulsion was fed to the reaction mixture over a period of 3hours together with an initiator solution (0.8 g NaPS except for C-4.6with 1.2 g, in 210 g of water). Upon completion of the feeds, thereaction mixture was maintained at the reaction temperature for 20minutes.

TABLE 4 Preparation of comparative examples PMAA- Comp. H₂O H₂O Surf.Surf. EA BA MMA BMA Sty. MMA mm⁽²⁾ Ex. #1 (g) #2 (g) #1⁽¹⁾ (g) #2⁽²⁾ (g)(g) (g) (g) (g) (g) (g) (g) C-4.1 400 525 22.3 14.6 130.5 750 361.5 —187.5 48 22.5 C-4.2 400 525 22.3 14.6 —   852.5 420   105 — — 22.5 C-4.3400 675 22.3 14.6 — 795 679.5 — — 25.5 — C-4.4 400 525 22.3 14.6 103.5690 289.5 — 373.5 21 22.5 C-4.5 400 525 22.3 14.6   75 765 210   — 412.515 22.5 C-4.6 1395  397 ⁽³⁾ 19.4 —   1116.8 615.6 — — — 26.3 C-4.7 400525 22.3 14.6 130.5 750 371.1 — 187.5 38.4 22.5 C-4.8 400 525 22.3 14.6130.5 750 390.3 — 187.5 19.2 22.5 C-4.9 400 525 22.3 14.6 130.5 750409.5 — 187.5 — 22.5 ⁽¹⁾Ethoxylated C₆ to C₁₈ alkyl ether sulfate havingfrom 1 to 40 ethylene oxide groups per molecule (30% active in water).⁽²⁾PMAA-MM (prepared by method of Example 2.1) ⁽³⁾15 g of an acryliclatex seed polymer at 30% solids and particle size of 90 nm was used.⁽⁶⁾The values listed for Examples C-4.7 to C-4.9 are the values onewould use in preparation of the corresponding acrylic copolymers.

Graft and Random copolymer compositions prepared in the previousexamples were characterized by various analytical techniques todetermine wt % solids, particle size, weight average molecular weight,number average molecular weight, and percent incorporation ofmacromonomer.

Determination of the amount of unreacted macromonomer was carried out byHPLC analysis using the following procedure. The copolymer compositionswere dissolved in THF and analyzed by gradient elution on an LC-18column supplied by Supelco, located in Bellefonte, Pa. such that awell-isolated peak was observed for the unreacted macromonomer.Quantification was carried out by calibrating the detector responseusing known standards of the same macromonomer employed in thesynthesis. The results of the characterization are reported in Table 5below.

TABLE 5 Characterization Of Copolymer Compositions Particle PMMA-MM SizeMw Mn Incorp.⁽¹⁾ Ex. % Solids (nm) (× 10⁻³) (× 10⁻³) (wt %) 3.1 44.5 117366.5 67.7 90 3.2 44.9 150 645 254.4 99 3.3 42.8 132 921.3 145.4 99 3.445.5 106 501.7 95.9 87 3.5 44.7 124 631.7 199.2 95 3.6 45.9 171 566141.4 95 3.7 45.2 105 815.7 132.4 90 3.8 43.9 109 610 147.6 84 3.9 46.4113 714.7 196.2 82 3.10⁽²⁾ 44 150 500 150 90 3.11⁽²⁾ 44 150 500 150 903.12⁽²⁾ 44 150 500 150 90 3.13 45.6 144 337.6 22.1 89 3.14 45.3 171340.4 18.7 — 3.15 45.8 119 229 108 91 C-4.1 45.3  96 91.6 3.1 — C-4.237.5  99 146.7 21.7 — C-4.3 47.3 103 148.0 27.5 — C-4.4 46.6  93 88.73.3 — C-4.5 45.4 107 299.3 51.9 — C-4.6 43.7 254 116.8 488.1 — C-4.7⁽²⁾44 100 150 50 — C-4.8⁽²⁾ 44 100 150 50 — C-4.9⁽²⁾ 44 100 150 50 —⁽¹⁾Based on the total weight of macromonomer added to reaction vessel.⁽²⁾The values listed for Examples 3.10-3.12 and C-4.7 through C-4.9 arethe values one would expect in the polymer products.

Example 5

Preparation of a Soft-Hard Elastormeric (SHE) Polymer (C-5.1)

The polymer was prepared by a three-stage polymerization process similarto that described in U.S. Pat. No. 6,060,532. The first stage wasconducted by semi-continuous emulsion polymerization in a 4-neck 5-literround-bottom flask equipped with a mechanical stirrer, temperaturecontrol device, initiator feed lines and a nitrogen inlet. Deionizedwater (704 g) was charged to the reaction flask and heated to 92° C. Amonomer emulsion containing 366 g of deionized water, 7.4 g ofsurfactant (A-16-22), 1370 g of BA and 20 g of acrylic acid was preparedin a separate flask. When the deionized water had reached 92° C., aninitiator solution (1.77 g of Ammonium Persulfate in 26 g of water) and67.2 g of a polymer seed (acrylic latex with total solid content of 45%and particle size of 90 nm) were introduced into the reaction flask withstirring. The monomer emulsion was fed to the reaction mixture over aperiod of about 2 hours, together with a initiator solution containing1.77 g of APS in 78 g of water. The polymerization temperature wasmaintain at 85° C. Upon completion of the feeds, the reaction mixturewas cooled to 60° C. Aqueous ammonium hydroxide (14% by weight) wasadded during the cooling followed by 4.1 g of an Fe₂SO₄ solution (0.2%).At 60° C., 3.8 g of t-butyl hydroperoxide (70%) in 46 g of water and2.45 g of Sodium sulfoxylate formaldehyde in 46 g of water were addedover a period of 45 minutes.

A second monomer emulsion containing 102 g of water, 1.85 g of Polystep™A-16-22, 359 g of MMA and 8.7 g of MAA was prepared. A solution ofPennstop 2697 (0.89 g supplied by Elf Atochem) in 30 g of water wasadded to the reaction mixture from stage 1. The monomer emulsion wasadded to the reaction mixture in one shot followed by 1.55 g of t-butylhydroperoxide (70%) in 3.7 g of water and 0.65 g of Sodium sulfoxylateformaldehyde in 33 g of water. The reaction mixture was held at the peakexotherm temperature (71-74° C.) for 5 minutes, and then cooled to 60°C.

A third monomer emulsion containing 102 g of water, 1.85 g of A-16-22,359 g of MMA and 8.7 g of MAA was prepared and add to the reactionmixture from stage 2 followed by 1.55 g of t-butyl hydroperoxide (70%)in 3.7 g of water and 0.65 g of Sodium sulfoxylate formaldehyde in 33 gof water. The reaction mixture was held at the peak exotherm temperature(71-74° C.) for 5 minutes and cooled to ambient temperature.

The final latex collected after passing through a 100 mesh filter wasanalyzed to have a solids level of 51.4% and particle size of 430 nm.

Example 6

Adjustment of Aqueous Dispersions to Similar Solids and pH for Use inPreparing Films

Portions of the example and comparative emulsions where diluted withdeionized water to 35% to 40% weight solids and neutralized with 28% NH₃to a pH of 8.0 to 8.5. In some examples, oligomer were also adjusted ina similar manner, and coalescing agent where added at the levelsdescribed in Table 6. These adjusted emulsions, indicated with an “a”suffix, were allowed to equilibrated at least overnight before furthertesting.

TABLE 6 Composition of the Polymer Portion of Aqueous Dispersion Tested.Pol. Pol. % Ex. Type Backbone Composition Graft Segment Olig. Coa. No.(1) (2) Composition (3) (4) 3.1a c/coa 65(78.2 BA/19.5 STY/2.3 g-MAA)35(70 MMA/25 EA/5 5 MAA) C- r/coa 50 BA/8.7 EA/24.1 MMA/12.5 Sty/3.2 54.1a MAA/1.5 g-MAA 3.1a c 65(78.2 BA/19.5 STY/2.3 g-MAA) 35(70 MMA/25EA/5 MAA) C- r 50 BA/8.7 EA/24.1 MMA/12.5 Sty/3.2 4.1a MAA/1.5 g-MAA3.2a c/o 78.8(97.7 BA/2.3 g-MAA) 21.2(100 MMA)⁽⁷⁾ (5) 5.1a sh 65 (98.6BA/1.4 AA)/35 (97.6 MMA/2.4 MAA) 3.3a c 65(97.7 BA/2.3 g-MAA) 35(100MMA)⁽⁷⁾ 3.4a c 65(97.7 BA/2.3 g-MAA) 35(100 MMA)⁽⁸⁾ C- r 63.5 BA/35MMA/1.5 MAA 4.6a 3.5a c 63.5 BA/1.5 g-MAA 35(80 MMA/20 BMA) C- r 63.5BA/28 MMA/7 BMA/1.5 g-MAA 4.2a 3.13a c/o 88.5 BA/1.5 g-MAA 10(100 MMA)(6) 3.7a c 54.2 BA/1.5 g-MAA 44.3(100 MMA) 4.3a r 53 BA/45.3 MMA/1.7 MAA3.8a c 72.5(63.6 BA/34.3 Sty/2.1 g-MAA) 27.5(70 MMA/25 EA/5 MAA) C- r46.2 BA/6.9 EA/19.3 MMA/24.9 4.4a Sty/1.4 MAA/1.5 MAA 3.9a c 80(63.8BA/34.3 Sty/1.9 g-MAA) 20(70 MMA/25 EA/5 MAA) C- r 51 BA/5 EA/14MMA/27.5 Sty/1 4.5a MAA/1.5 g-MAA 3.1a c 65(78.2 BA/19.5 STY/2.3 g-MAA)35(70 MMA/25 EA/5 MAA) C- r 50 BA/8.7 EA/24.1 MMA/12.5 Sty/3.2 4.1aMAA/1.5 g-MAA 3.10a⁽⁹⁾ c 65(78.2 BA/19.5 STY/2.3 g-MAA) 35(71 MMA/25EA/4 MAA) C- r 50 BA/8.7 EA/24.7 MMA/12.5 Sty/2.6 4.7a⁽⁹⁾ MAA/1.5 g-MAA3.11a⁽⁹⁾ c 65(78.2 BA/19.5 STY/2.3 g-MAA) 35(73 MMA/25 EA/2 MAA) C- r 50BA/8.7 EA/26 MMA/12.5 Sty/12.8 4.8a⁽⁹⁾ MAA/1.5 g-MAA 3.12a⁽⁹⁾ c 65(78.2BA/19.5 STY/2.3 g-MAA) 35(75 MMA/25 EA) C- r 50 BA/8.7 EA/27.3 MMA/12.5Sty/1.5 4.9a⁽⁹⁾ g-MAA ⁽¹⁾Used in the tables herein, the followingabbreviations have these meanings: “disp.” = “aqueous dispersion”; “ex.”= “example”; “no.” = “number”; “pol.” = “polymer”; “r” = “randomcopolymer”; “c” = “comb copolymer”; “sh” = SHE copolymer; “c/coa” =“comb copolymer” plus “coalescent” at 5 weight %; “r/coa” = “ randomcopolymer” plus “coalescent” at 5 weight %; “c/o” = “combcopolymer/oligomer” blend; “g-MAA” = “grafted MAA macromonomer”; “olig.”= “oligomer”; and “coa.” = “coalescent”. ⁽²⁾When the polymer is a combcopolymer, the numbers inside the parentheses sum to 100 and representthe weight percent of monomer, present as polymerized units, based onthe weight of the backbone polymer. The number preceding the openparenthesis is the weight percent of backbone polymer, based on thetotal weight of the comb copolymer. For random copolymers, thecomposition of the entire polymer is listed under “backbone”, and noparentheses are required. ⁽³⁾When the polymer is a comb copolymer, thenumbers inside the parentheses sum to 100 and represent the weightpercent of monomer, present as polymerized units, based on the weight ofthe graft segment. The number preceding the open parenthesis is theweight percent of graft segment, based on the total weight of the combcopolymer. ⁽⁴⁾The coalescent, DOWANOL ™ PPh (available from Dow Chemicalof Midland, Michigan), was added to the aqueous dispersion at 5 weightpercent, based on the weight of polymer solids. DOWANOL ™ PPh is propylphenyl glycol ether. ⁽⁵⁾The oligomer, prepared in Example 1.5, is amacromonomer which is a homopoloymer of MMA, having an Mn = 3,800, andan Mw = 5,400. The weight ratio of comb copolymer to oligomer is 80:20.⁽⁶⁾The oligomer, prepared in Example 1.5, is a macromonomer which is ahomopoloymer of MMA, having an Mn = 3,800, and an Mw = 5,400. The weightratio of comb copolymer to oligomer is 58:42. ⁽⁷⁾The graft segment hasan Mn = 3,800 and an Mw = 5,400. ⁽⁸⁾The graft segment has an Mn = 11,200and an Mw = 16,700. ⁽⁹⁾The values listed for Examples 3.10a through3.12a and C-4.7a through C-4.9a are the values one would use inpreparation of the corresponding acrylic graft copolymers (i.e., combcopolymer).

TABLE 7 Glass transition temperatures for the copolymers as calculatedusing the Fox Equation. Tg Tg Tg With Pol. Back- Graft Tg % CoalescingEx. Pol. bone segment Overall Coalescing Agent⁽¹⁾, No. Type (° C.) (°C.) (° C.) agent ° C. 3.1a c/coa −32 65 −5 5 −10 C- r/coa −5 5 −10 4.1a3.1a c −32 65 −5 C- r −5 4.1a 3.2a c/o −51 105  −11  5.1a sh −15  3.3a c−51 105  −14  3.4a c −51 105  −14  C- r −14  4.6a 3.5a c −51 84 −17  C-r −17  4.2a 3.13a c/o −52 105    3 3.7a c −51 105    0 4.3a r   1 3.8a c−15 65   4 C- r   3 4.4a 3.9a c −15 65 −2 C- r −2 4.5a 3.1a c −32 65 −5C- r −5 4.1a 3.10a⁽²⁾ c −32 65 −5 C- r −5 4.7a⁽²⁾ 3.11a⁽²⁾ c −32 66 −5C- r −5 4.8a⁽²⁾ 3.12a⁽²⁾ c −32 66 −5 C- r −5 4.9a⁽²⁾ ⁽¹⁾Using Tg = −75°C. for the coalescent. ⁽²⁾The values listed for Examples 3.10-3.12 andC-4.8 through C-4.10 are the values one would expect in the polymerproducts.

Method to Prepare Films

Films were prepared by using the method described in Producing Films ofUniform Thickness of Paint, Varnish, and Related Products on TestPanels, ASTM D 823-95, with the modifications detailed below.

For films applied to aluminum (Panel 3003, supplied by ACT Industries,Inc.; Milwaukee, Wis.) and polyethylene panels, Practice E was employed(Hand-Held Blade Film Application). For the aluminum panels, the desireddried film thickness was 50.8 um (2 mils). These films were used forKonig Hardness Pendulum Damping Test, Finger Tack Test, and Mandrel BendTest. For the polyethylene panels, the desired dried film thickness was101.6 um (4 mils). The polyethylene panels were treated with MoldRelease Agent (Crown, 6075) to facilitate the removal of the dried filmwith minimum distortion. These films were used for Tensile PropertiesTest.

For films applied to White Paper panels (Chart Form WB, supplied byLeneta Company, 15 Whitney Road, Mahwah, N.J.), Practice C was employed(Motor-Driven Blade Film Application). The desired dried film thicknesswas 25.4 um (1 mil). An auxiliary flattening bar was not used. Thesefilms were used for Block Testing.

The gap opening of the blade was chosen using the followingapproximation:

Gap Opening≈(Film Thickness×2)÷% Solids.

Drawdowns were either made in a Constant Temperature and Humidity Roomor the panels were placed in the room while still wet. The roomconditions were 23±2° C. and 65±5% Relative Humidity. Samples were driedfor at least 7 days before testing. If the samples contained coalescent,they were dried for 3½ days as noted above and then 3½ days in a vacuumchamber at <0.69 kPa (=0.1 pound/inch²) with a small bleed valve open tothe atmosphere, providing an air sweep of the chamber. The films werethen returned to the Constant Temperature and Humidity Room for at least3 hours before testing.

Method to Measure Film Thickness

In order to verify that the blade gap could be used as a good estimateof dry film thickness over all substrates, thickness values for severaldry films on aluminum panels were determined using the method describedin Measurement of Dry-Film Thickness of Organic Coatings UsingMicrometers, ASTM D 1005-95, as detailed in Procedure A, 6.1.5. Thesemeasurements agreed to within 15% of those estimated from Equation 1above. For the films on polyethylene panels used in Tensile PropertiesTest, the thicknesses of free films were determined using Procedure B.

Konig Pendulum Hardness

The Konig Hardness of films were determined using Method for Hardness ofOrganic Coatings by Pendulum Damping Tests, ASTM D 823-95, with themodifications detailed below.

Dry films were prepared as described above. The Konig Pendulum Hardness,Test Method A, was determined for the films using an oscillation counteras described in Note 1.

Tensile Properties Test

The Tensile Properties of free films were determined using Method forTensile Properties of Organic Coatings, ASTM D 2370-98, with themodifications detailed below.

Dry films were prepared on polyethylene panels as described above. Afterdrying, the top surface of the film was treat with the same mold releaseagent as used in the film casting. For very tacky films, a light dustingof talc was also applied with a camel hair brush. The edges were tapedto reinforce the film and it was slowly removed from the panel. If thesample adhered to the panel, it was chilled with ice or dry ice prior toremoving. Samples were cut with a scalpel and template to a dimension of1.27 cm (½ inch) by 7.62 cm (3 inch). The top and bottom 2.54 cm (1inch) was reinforced with masking tape leaving a gage length of 2.54 cm(1 inch). Specimens were discarded if they displayed visible flaws,scratches, nicks, tears, or other imperfections likely to causepremature failure during Tensile Property Testing. The thickness ofthese free films was determined as described above.

The samples were tested in a room with the same temperature and relativehumidity as that in which they were conditioned. The crosshead speed was2.54 cm/minute (1 inch/minute) or 100%/minute for the gage lengthchosen. The elongation is measured at the point of rupture. The tensilestrength is measured at the maximum value. At least 2 samples weretested for each sample. Spurious values were discarded as described in12.2.2.

Test Method: Finger Tack

Tack is the “stickiness” of the surface of a material. It can bequalitatively measured by Finger Tack which is the ability of thematerial to stick to a clean, dry finger. While subjective it does givea good, reproducible rating of Tack.

Finger Tack is tested by lightly pushing your freshly washed and driedfinger on the film on the end of an Aluminum panel, prepared asdescribed above, and slowly lifting your hand until the panel falls. Theposition of the panel when it falls yields the rating (Table 8).

TABLE 8 Rating system for the Finger Tack Test. Tack Position When PanelFalls Rating Rating panel does not lift at all None 5 up to ˜30° Slight4 above 30° but before panel lifts Moderate 3 off the surface panelfalls as it lifts from the surface Very 2 panel is lifted off thesurface Extreme 1

Test Method: Peel Block Resistance

The Peel Block Resistance test was used for rating the resistance ofpaint films to blocking, i.e., sticking or fusing when they are placedin contact with each other. ASTM Test Method D4946-89 (Reapproved 1999),Standard Test Method for Blocking Resistance of Architectural Paints,was followed using a temperature of 48.9° C. (120° F.).

The samples were rated for block resistance on a scale of 0 to 10. Blockresistance is reported on a numerical scale of 0 to 10, whichcorresponds to a subjective tack and seal rating determined by theoperator. This rating system is defined below in appropriate descriptiveterms (Table 9).

TABLE 9 Rating Scale for Block Resistance Test. Seal as percent RatingDescription Tack of contact area 10 perfect none none 9 excellent tracenone 8 Very good slight none 7 Good slight none 6 Good moderate none 5Fair moderate none 4 Fair severe none 3 Poor  5-25% 2 Poor 25-50% 1 Poor50-75% 0 Very poor 100%

For purposes of calculation of the Block Advantage value, A_(B), thescale of Table 9 and ASTM Standard Test Method D4946-89 was modified toa 1 to 5 scale. Ratings of 0, 1, and 2 are reported as 1; 3 and 4 as 2;5 and 6 as 3; 7 and 8 as 4; and 9 and 10 as 5.

Test Method: Low Temperature Flexibility via Mandrel Bend Test

The low temperature flexibility of films was determined by using theMandrel Bend Test of Attached Organic Coatings, ASTM D522-93a, with themodifications detailed below.

Films on Aluminum panels were prepared as previously described. Thethickness of several random samples was determined with a dialmicrometer gauge. They were 50.8±7.6 μm (2±0.3 mils), so the targetvalue of 50.8 μm (2 mils) was used in the calculation of % elongation.Test strips were cut from the original panels to a size of 2.54 cm×10.16cm (1 inch by 4 inch). These strips and test equipment were conditionedat −35° C., or −10° C., for 4 hours prior to testing.

Test Method B, the Cylindrical Mandrel Test, was used to determine theelongation of the film. In addition to the specified test equipment,5.08 cm (2 inch) and 10.16 (4 inch) cm diameter steel tubes were used.The bend time was 1 second instead of the 15 second bend time specifiedfor elongation measurements. No correction was attempted for thedifference in bend rate.

The % Elongation and Correction Factors for the 5.08 cm (2 inch) and10.16 cm (4 inch) diameter mandrels were linearly extrapolated on alog-log plot from those at 2.54 cm and smaller diameter and are given inTable 10. The calculated Total Elongation for 50.8 μm films is alsogiven.

TABLE 10 Elongation, Correction for Film thickness, and Total ElongationMandrel Mandrel Correction Total elongation diameter diameter Elongationfor film for 50.8 (cm) (inches) (%) thickness μm films (%) 0.318 .12528.00 1.40 30.8 0.635 .250 14.00 0.71 15.4 1.27 .500 6.75 0.38 7.5 2.541 3.30 0.21 3.7 5.08 2 1.60 0.11 1.8 10.16 4 0.78 0.06 0.9

The test results for the film properties as described above are given inTable 11.

TABLE 11 Results for Tests of Hardness and Softness. Block⁽¹⁾ Mandrel48.9° C. Elongation Pol. Tensile (120° F.) Elongation At Ex. Pol.Strength 30 at 23° C. −35° C.⁽²⁾ No. Type Konig(s) Tack (kPa) minutes(%) (%) 3.1a c/coa 21.0 5 5,350 2 410 30.8 C-4.1a r/coa 4.2 1 2,765 1664 0.9 3.1a c 18.9 4 5,343 1 421 3.7 C-4.1a r 8.4 2 6,267 1 756 1.83.2a c/o 8.4 1 2,710 1 534 30.8 5.1a sh 8.4 2 1,255 1  92 7.5 3.3a cpoor poor poor poor poor poor film film film film film film 3.4a c poorpoor poor poor poor poor film film film film film film C-4.6a r 7.0 11,634 1 1,119   3.7 3.5a c 26.6 5 3,185 4 104 30.8 C-4.2a r 5.6 1   7861 1,107   7.5 3.13a c/o 11.2 4 2,717 2 593 30.8 3.7a c poor poor poorpoor poor poor film film film film film film 4.3a r 17.5 4 4,309 1 3871.8 3.8a c 23.8 5 7,619 2 403 1.8 C-4.4a r 22.4 4 5,936 1 430 0.9 3.9a c14.0 4 5,212 1 389 3.7 C-4.5a r 8.4 2 3,923 1 728 1.8 3.1a c 18.9 45,343 1 421 3.7 C-4.1a r 8.4 2 6,267 1 756 1.8 3.10a⁽³⁾ c 18.9 4 5,343 1421 3.7 C-4.7a⁽³⁾ r 8.4 2 6,267 1 756 1.8 3.11a⁽³⁾ c 18.9 4 5,000 1 4003.7 C-4.8a⁽³⁾ r 8.4 2 6,267 1 756 1.8 3.12a⁽³⁾ c 18.9 4 4,500 1 375 3.7C-4.9a⁽³⁾ r 8.4 2 6,267 1 756 1.8 ⁽¹⁾The test method for “blockresistance” (supra) rates block resistance on a scale of 0 to 10 with 0being “very poor” and 10 being “perfect”. For purposes of calculation ofthe Block Advantage value, A_(B), the scale was modified to a 1 to 5scale in Table 11. Ratings of 0, 1, and 2 are reported as 1; 3 and 4 as2; 5 and 6 as 3; 7 and 8 as 4; and 9 and 10 as 5. ⁽²⁾Dispersion Examples3.8a and 3.9a and Comparatives C-4.4a and C-4.5a were tested at −10° C.to assure that the test temperature was lower than the calculatedaverage Tg of the polymers. ⁽³⁾The values listed for Examples 3.10athrough 3.12a and C-4.7a through C-4.9a are the values one would expectin the polymer products.

The calculated Advantage Values for the individual Advantage Termsdescribed above are given in Table 12.

TABLE 12 Advantage Values. Measures of Measures of Pol. HardnessSoftness Ex. Pol. A_(K) A_(T) A_(S) A_(B) A_(E) A_(F) No. Type (%) (%)(%) (%) (%) (%) 3.1a c/coa 400 400 94 100 −38 3322 C-4.1a r/coa 0 0 0 00 0 3.1a c 125 100 −15 0 −44 106 C-4.1a r 0 0 0 0 0 0 3.2a c/o 20 0 66 0−52 732 5.1a sh 20 100 −23 0 −92 103 3.3a c −100 −100 −100 −100 −100−100 3.4a c −100 −100 −100 −100 −100 −100 C-4.6a r 0 0 0 0 0 0 3.5a c375 400 305 300 −91 311 C-4.2a r 0 0 0 0 0 0 3.13a c/o −36 0 −37 100 531611 3.7a c −100 −100 −100 −100 −100 −100 4.3a r 0 0 0 0 0 0 3.8a c 6 2528 100 −6 100 C-4.4a r 0 0 0 0 0 0 3.9a c 67 100 33 0 −47 106 C-4.5a r 00 0 0 0 0 3.1a c 125 100 −15 0 −44 106 C-4.1a r 0 0 0 0 0 0 3.10a⁽¹⁾ c125 100 −15 0 −44 106 C-4.7a⁽¹⁾ r 0 0 0 0 0 0 3.11a⁽¹⁾ c 125 100 −20 0−47 106 C-4.8a⁽¹⁾ r 0 0 0 0 0 0 3.12a⁽¹⁾ c 125 100 −28 0 −50 106C-4.9a⁽¹⁾ r 0 0 0 0 0 0 ⁽¹⁾The values listed for Examples 3.10a-3.12aand C-4.7a through C-4.9a are the values one would expect in the polymerproducts.

The Advantage Values cumulative Hard, Soft and Hard/Soft BalanceAdvantage Terms as described below are given in Table 13.

TABLE 13 Advantage Values: Average Hardness, Softness, and Hard/SoftBalance⁽¹⁾. Pol. Ex. Pol. A_(Hard) A_(Soft) A_(HSB) No. Type (%) (%) (%)3.1a c/co 248 1,642 945 a C-4.1a r/co 0 0 0 a 3.1a c 53 31 42 C-4.1a r 00 0 3.2a c/o 21 340 181 5.1a sh 24 5 15 3.3a c −100 −100 −100 3.4a c−100 −100 −100 C-4.6a r 0 0 0 3.5a c 345 110 228 C-4.2a r 0 0 0 3.13ac/o 7 832 419 3.7a c −100 −100 −100 4.3a r 0 0 0 3.8a c 40 47 43 C-4.4ar 0 0 0 3.9a c 50 29 40 C-4.5a r 0 0 0 3.1a c 53 31 42 C-4.1a r 0 0 03.10a⁽²⁾ c 53 31 42 C- r 0 0 0 4.7a⁽²⁾ 3.11a⁽²⁾ c 51 29 40 C- r 0 0 04.8a⁽²⁾ 3.12a⁽²⁾ c 49 28 38 C- r 0 0 0 4.9a⁽²⁾ ⁽¹⁾A_(Hard) = (A_(K) +A_(T) + A_(S) + A_(B))/4 A_(Soft) = (A_(E) + A_(F))/2 A_(HSB) =(A_(Hard) + A_(Soft))/2. ⁽²⁾The values listed for Examples 3.10a through3.12a and C-4.7a through C-4.9a are the values one would expect in thepolymer products.

The values of the Advantage terms on the right side of each of theseequations are listed in Table 13.

The values of the Hard/Soft Balance Advantage terms, A_(HSB), of Table13 show that the comb copolymers of the present invention display animprovement in the balance of hardness and softness of at least 25% whencompared with random copolymers having the same overall composition. Acomparison of a SHE copolymer with a comb copolymer further revealsperformance of the comb copolymer which is superior to that of the SHEcopolymer (15%) having the same composition.

Example 7

Adjustment of Aqueous Dispersions to Similar Solids and pH for Use inPreparing Films

Portions of the example and comparative aqueous dispersions wherediluted with deionized water to 35% to 40% weight solids and neutralizedwith 28% NH₃ to a pH of 8.0 to 8.5. These adjusted emulsions, asindicated by the “a” suffix, were allowed to equilibrated at leastovernight before further blending or testing. Film preparation andtesting were done as described above.

TABLE 14 Composition of the Polymer Portion of Aqueous DispersionTested. Pol. Pol. Graft Segment Ex. Type Composition No. (1) BackboneComposition (2) (3) 3.4a c 65(97.7 BA/2.3 g-MAA) 35(100 MMA) 3.14a c98(98.5 BA/1.5 g-MAA)  2(100 MMA) 3.15a c 80(98.1BA/1.9g-MAA) 20(100MMA) 3.16a⁽⁴⁾ c/c ⁽¹⁾Used in the tables herein, the followingabbreviations have these meanings: “disp.” ≡ “aqueous dispersion” notused????; “ex.” “example”; “no.” ≡ “number”; “pol.” ≡ “polymer”; “r” ≡“random copolymer”; “c” ≡ “comb copolymer”; “c/c” ≡ “a blend comprisingat least 2 comb copolymers”; “sh” ≡ SHE copolymer; #“c/coa” ≡ “combcopolymer” plus “coalescent” at 5 weight %; “r/coa” ≡ “random copolymer”plus “coalescent” at 5 weight % “r/coa” ≡“random copolymer” plus“coalescent” at 5 weight % ; “c/o” ≡ “comb copolymer / oligomer” blend;“g-MAA” ≡“grafted MAA macromonomer”; “olig.” ≡“oligomer”; and “coa.” ≡“coalescent”. ⁽²⁾When the polymer is a comb copolymer, the numbersinside the parentheses sum to 100 and represent the weight percent ofmonomer, present as polymerized units, based on the weight of thebackbone polymer. The number preceding the open parenthesis is theweight percent of backbone polymer, based on the total weight of thecomb copolymer. For random copolymers, the composition of the entirepolymer is listed under “backbone”, and no parentheses are required.⁽³⁾When the polymer is a comb copolymer, the numbers inside theparentheses sum to 100 and represent the weight percent of monomer,present as polymerized units, based on the weight of the graft segment.The number preceding the open parenthesis is the weight percent of graftsegment, based on the total weight of the comb copolymer. ⁽⁴⁾Example3.16a is a blend of 45.5% of Example 3.14a with 55.5% of Example 3.4ayielding an average composition equivalent to Example 3.15a.

TABLE 15 Results for Tests of Hardness and Softness. Block⁽¹⁾ Mandrel48.9° C. Elongation Pol. Tensile (120° F.) Elongation At Ex. Pol.Strength 30 at 23° C. −35° C. No. Type Konig(s) Tack (kPa) minutes (%)(%) 3.4a c poor poor poor poor poor poor film film film film film film3.14a c  9.8 2   579 1 537 30.8 3.15a c 11.7 4 1,400 2 482 30.8 3.16ac/c 12.1 4 1,586 1 717 30.8 ⁽¹⁾The test method for “block resistance”(supra) rates block resistance on a scale of 0 to 10 with 0 being “verypoor” and 10 being “perfect”. For purposes of calculation of the BlockAdvantage value, A_(B), the scale was modified to a 1 to 5 scale inTable 15. Ratings of 0, 1, and 2 are reported as 1; 3 and 4 as 2; 5 and6 as 3; 7 and 8 as 4; and 9 and 10 as 5.

The results of film testing are given in Table 15. No Advantage Valuesare calculated since a common control is not possible over the series ofexamples as the macromonomer level was changed. Comparisons made byinspection of the data show that blending two comb copolymers whichformed a poor film (Example 3.4a) and which had relatively poorperformance (Example 3.16a) give a dispersion (Example 31.6a) yielding afilm with performance superior to either component. The blend also hasperformance better than the performance of a comb copolymer ofequivalent overall composition (example 3.15a). In these examples,macromonomer level was varied. Similar results are anticipated forvarying macromonomer, oligomer, and backbone composition and level, Tg,hydrophilicity, and molecular weight as well as particle size of theindividual comb copolymers or oligomer dispersions. One or more of theblend components could be a polymer other than a comb-copolymer.

We claim:
 1. An aqueous dispersion, comprising a plurality of waterinsoluble segmental copolymer particles, wherein said particles comprisecomb copolymer, and wherein said comb copolymer comprises: (a) from 2weight percent to 90 weight percent of macromonomer, as polymerizedunits, based on the total weight of said comb copolymer, wherein: (i)said macromonomer is water insoluble and comprises from 10 to 1000polymerized units of at least one first ethylenically unsaturatedmonomer, no polymerized mercapto-olefin compounds, and less than 5weight percent polymerized acid-containing monomer; (ii) saidmacromonomer has a molecular weight distribution such that its ratio ofMw/Mn is at least 1.25, wherein said Mw is the weight average molecularweight of the macromonomer and said Mn is the number average molecularweight of said macromonomer; and (iii) said macromonomer is amacromonomer prepared by aqueous based polymerization; and (b) from 10weight percent to 98 weight percent of polymerized units of at least onesecond ethylenically unsaturated monomer, based on the total weight ofsaid comb copolymer.
 2. The aqueous dispersion of claim 1, wherein saidaqueous dispersion has a Hard/Soft Balance Advantage value of at least25%.
 3. The aqueous dispersion of claim 1: wherein said comb copolymercomprises a backbone and at least one graft segment; wherein said graftsegment is derived, as a polymerized unit, from said macromonomer; andwherein said comb copolymer is present as a plurality of comb copolymerparticles.
 4. The aqueous dispersion of claim 3, wherein said combcopolymer has a weight average molecular weight of 50,000 to 2,000,000.5. The aqueous dispersion of claim 3, wherein said graft segmentcomprises, as polymerized units, less than 1 weight percent acidcontaining monomer, based on the total weight of said macromonomer. 6.The aqueous dispersion of claim 3, wherein said graft segment contains,as polymerized units, at least one unit derived from a non-methacrylatemonomer.
 7. The aqueous dispersion of claim 3, wherein said graftsegment comprises, as polymerized units, from 5 weight percent to 50weight percent of a non-methacrylate monomer, based on the weight ofsaid macromonomer.
 8. The aqueous dispersion of claim 3, wherein saidgraft segment has a degree of polymerization of from 10 to less than 50,where the degree of polymerization of said graft segment is expressed asthe degree of polymerization of said macromonomer.
 9. The aqueousdispersion of claim 3, wherein said graft segment has a glass transitiontemperature of 30° C. to 130° C.
 10. The aqueous dispersion of claim 3,wherein said backbone has a glass transition temperature of −90° C. to50° C.
 11. The aqueous dispersion of claim 3, wherein said graft segmentis present in the amount of 1 to 70 weight percent based on the weightof said comb copolymer.
 12. The aqueous dispersion of claim 3, furthercomprising a coalescent in an amount of from 0 weight percent to 40weight percent, based on the weight of said comb copolymer.
 13. Theaqueous dispersion of claim 3, further comprising an oligomer in anamount of 1 to 50 weight percent, based on the weight of said combcopolymer.
 14. The aqueous dispersion of claim 3, wherein said combcopolymer is produced by a polymerization method comprising the stepsof: (a) forming a macromonomer aqueous emulsion comprising a pluralityof water-insoluble particles of macromonomer, wherein said macromonomercomprises polymerized units of at least one first ethylenicallyunsaturated monomer, said macromonomer further having: (i) a degree ofpolymerization of from 10 to 1000; (ii) at least one terminalethylenically unsaturated group; (iii) less than 5 weight percentpolymerized acid-containing monomer, based on the weight of saidmacromonomer; (iv) no polymerized mercaptan-olefin compounds; and (v)said macromonomer has a molecular weight distribution such that itsratio of Mw/Mn is at least 1.25, wherein said Mw is the weight averagemolecular weight of the macromonomer and said Mn is the number averagemolecular weight of said macromonomer; (b) forming a monomer compositioncomprising at least one second ethylenically unsaturated monomer; and(c) combining at least a portion of said macromonomer aqueous emulsionand at least a portion of said monomer composition to form apolymerization reaction mixture; and (d) polymerizing said macromonomerwith said second ethylenically unsaturated monomer in the presence of aninitiator to produce said plurality of comb copolymer particles.
 15. Theaqueous dispersion of claim 14, wherein said polymerization reactionmixture further comprises a macromolecular organic compound.
 16. Amethod of forming a film comprising the steps of: (a) forming amacromonomer aqueous emulsion comprising a plurality of water-insolubleparticles of macromonomer, wherein said macromonomer comprisespolymerized units of at least one first ethylenically unsaturatedmonomer, said macromonomer further having: (i) a degree ofpolymerization of from 10 to 1000; (ii) at least one terminalethylenically unsaturated group; (iii) less than 5 weight percentpolymerized acid-containing monomer, based on said macromonomer; (iv) nopolymerized mercaptan-olefin compounds; (v) a molecular weightdistribution such that its ratio of Mw/Mn is at least 1.25, wherein saidMw is the weight average molecular weight of the macromonomer and saidMn is the number average molecular weight of said macromonomer; and (vi)said macromonomer is a macromonomer prepared by aqueous basedpolymerization; (b) forming a monomer composition comprising at leastone second ethylenically unsaturated monomer; (c) combining at least aportion of said macromonomer aqueous emulsion and at least a portion ofsaid monomer composition to form a polymerization reaction mixture; (d)polymerizing said macromonomer with said second ethylenicallyunsaturated monomer in the presence of an initiator to produce anaqueous dispersion comprising a plurality of water-insoluble combcopolymer particles; (e) applying said aqueous dispersion to asubstrate; and (f) drying, or allowing to dry, said applied aqueousdispersion, wherein said comb copolymer comprises: from 2 weight percentto 90 weight percent of said macromonomer, as polymerized units, basedon the total weight of said comb copolymer; and from 10 weight percentto 98 weight percent of said second ethylenically unsaturated monomer,as polymerized units, based on the total weight of said comb copolymer.17. The method of claim 16, wherein said polymerization reaction mixturefurther comprises a macromolecular organic compound.
 18. A film producedby the method of claim
 16. 19. The method of claim 16 wherein saidaqueous dispersion has a Hard/Soft Balance Advantage value of at least25%.